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View Full Version : Engine is bogging down on hole shot


nrojay
07-21-2013, 01:19 AM
95' Prostar 190 LT1

Today we had some issues, during hole shot the engine would bogg down even at full throttle for several yards and then it would come back to life and run out ok. but once we would stop and change skiers the same issue would come back. Also when I go to put it in gear the transmision would start making an awefull noise and would vibrate, but once the engine would take off it ran smooth. I started running it out after being stopped for awhile just to keep it from doing the problem

I just had it in the shop having the oil, filter, Main circulating pump replaced along with water impellor.

It actually started doing this last weekend, but after reading several post on here I decided to look at the fuel pump inlet screen, which is on the back of engine. I took it off and discovered alot of lint like material in it and pieces of trash in screen. I changed the fuel filter and took the pickup screen inside the fuel cell out as well and cleaned it up. I really thought I had found the issue.

Temperature stayed around 150, I also changed the upper and lower thermostats out using the 140 degree and the 160 degree drilled stats.

Your advice is appreciated !

mikeg205
07-21-2013, 09:12 AM
Check fuel pressure at fuel rail - fuel pump maybe going bad - Rockauto has them for $84... usable for both LT1 and TBI 350.

http://www.rockauto.com/catalog/raframecatalog.php?catalog=26&partnum=P60987&a=FR26-P60987-88113

cmarty123
07-21-2013, 09:30 AM
My 350 tbi started doing this a couple years ago. I told the guys at SKIDIM about it and he said it sounded like my distributor was corroded and I need a new one. I ordered it and sure enough it fixed it.

cmarty123
07-21-2013, 12:48 PM
Sorry I forgot a word. I met to say distributer cap. Mine was $23.

nrojay
07-21-2013, 02:38 PM
i also noticed black smoke and the heavy smell of gas at the rear during the time it was doing this episode

mikeg205
07-21-2013, 02:44 PM
First thing I would do is pull the plugs and see what they look like. Then do a leak down test/ compression test. If these look good hopefully ECM stored some codes. Could also be a faulty ignition control module - Rockman here had some issues with that. I believe you have the Cadillac Northstar ingnition module where the coil pack attach onto. Maybe a loos connection there as well.

JimN
07-21-2013, 02:53 PM
i also noticed black smoke and the heavy smell of gas at the rear during the time it was doing this episode

Coolant temperature sensor- it has one yellow wire and one black wire.

JimN
07-21-2013, 02:54 PM
Sorry I forgot a word. I met to say distributer cap. Mine was $23.

No disctributor- if you're familiar with the 3.8L GM engines with the coil packs- it looks like that, but has four coils instead of three.

nrojay
07-21-2013, 03:45 PM
Exactly where is it located on the engine?
if it is a coolant sensor, would it be something that is sporadic, like it is doing ?

JimN
07-21-2013, 04:29 PM
Exactly where is it located on the engine?
if it is a coolant sensor, would it be something that is sporadic, like it is doing ?

Could be sporadic, but it's one of the only things that makes it run rich when it's hot. If the engine has overheated badly, the harness could be melted and if the ECT (Engine Coolant Temperature) wires short together or the yellow shorts to the block, it will make the ECM think the engine is overheating. Since this isn't the symptom, I would conclude that it's a bad sensor but you should verify the fault before starting to throw parts at it. Sorry, too late to stop the "parts cannon"- you already fired it up. If you want to do the work on this engine, and this applies to EVERYONE who owns a boat, learn about how it works. If you know nothing about electronics/electricity, it's gonna be a long effing day because these use ONLY electronics to keep the engine running correctly. There's no centrifugal advance weights/springs, it doesn't physically use vacuum to draw more gas into a carb's barrels and it doesn't have a choke thermostat to help start it when it's cold. The fuel/air mix is controlled by the ECM, but what it delivers is based on throttle position, MAP sensor, engine speed and coolant temperature.

You used a Chevy LT-1 circulating pump, right? That's absolutely mandatory.

The engine temperature isn't what the ECM sees. The ECM is connected to the two wire sensor I mentioned before. The engine doesn't have so many sensors that you shouldn't explore and find out for yourself. You should be more familiar with it, anyway. Also, I would advise reading as much about this engine as possible- it's not like the others.

nrojay
07-21-2013, 04:55 PM
yes I see it on the front of the pump, I had the shop replace the circulating pump, could I use an ohm meter to check the sensor out or how do you check it.

Before I replaced the 2 thermostats it had gotten hot180 degrees and the ecm put the engine in limp mode, I shut it down and removed the top thermostat which by the way was not drilled out its the one the shop had replaced when they did the circulating pump.

So I contacted Mastercraft and ordered the correct stats for the motor

Yes it only makes since it could be the sensor still saying its running hot when its not

Just need to know how to test it and keep the cannon from firing LOL

JimN
07-21-2013, 05:16 PM
yes I see it on the front of the pump, I had the shop replace the circulating pump, could I use an ohm meter to check the sensor out or how do you check it.

Before I replaced the 2 thermostats it had gotten hot180 degrees and the ecm put the engine in limp mode, I shut it down and removed the top thermostat which by the way was not drilled out its the one the shop had replaced when they did the circulating pump.

So I contacted Mastercraft and ordered the correct stats for the motor

Yes it only makes since it could be the sensor still saying its running hot when its not

Just need to know how to test it and keep the cannon from firing LOL

If it's running rich, it's not from the sensor telling the ECM that it's hot, it would be from telling it that the engine is cold. Hot engines need less fuel to run efficiently. If you measure the sensor's resistance, it should be well less than 1K Ohms. If it's higher than that when the engine is cold, replace it. If you want to test it before replacing, measure the resistance, put it in hot water and re-test. If the resistance doesn't change or it increases far more, replace it. I already posted the resistance chart about 100 times, but I don't think the mods made it a sticky, as I requested. You can also google "GM ECT resistance chart".

nrojay
07-21-2013, 05:54 PM
ok I just pulled the sensor and checked the resistance across terminals and it is at 6ohms cold and when I put it under 120 degree hot water from kitchen sink it goes down to 4 ohms ?

I will also add that when the shop mechanic pulled the old pump he said there was no thermostat installed, so previous owner must of had issues .

JimN
07-21-2013, 08:41 PM
ok I just pulled the sensor and checked the resistance across terminals and it is at 6ohms cold and when I put it under 120 degree hot water from kitchen sink it goes down to 4 ohms ?

I will also add that when the shop mechanic pulled the old pump he said there was no thermostat installed, so previous owner must of had issues .

That's way off- and this was the two wire sensor and was it disconnected? I'm surprised it would start cold.

Here's the chart AGAIN, if the mods want to make it sticky-
http://www.explorerforum.com/photopost/data/503/medium/0900823d80191f99.gif

nrojay
07-21-2013, 11:10 PM
Yes it was disconnected, I will stop by Oreilys tomorrow and test a new one as well
I HOPE THIS IS THE PROBLEM!!

I read also on another post it could be something with the crank sensors.

However im going to chase this rabbit and hope its the problem, ill post results tomorrow

nrojay
07-22-2013, 04:51 PM
picked up new part checked ohms and it is measuring at room temp 9.5ohms while the old sensor is around 6ohms
i will try it out this week and report back my findings

nrojay
07-22-2013, 04:57 PM
JimN
would I need to reset the ECM or is it possible

André
07-22-2013, 04:57 PM
picked up new part checked ohms and it is measuring at room temp 9.5ohms while the old sensor is around 6ohms
i will try it out this week and report back my findings
Not sure how you are measuring but i also checked mine today and the readings were spot on with the chart JimN posted...
9.5 ohms is a bit out of range.:confused:
Room temp should be around 3000 ohms...

JimN
07-22-2013, 05:29 PM
picked up new part checked ohms and it is measuring at room temp 9.5ohms while the old sensor is around 6ohms
i will try it out this week and report back my findings

That can't be the correct part. If you compare its resistance with the chart, it's nowhere close to the correct value.

If the plug you pulled off of the sensor doesn't look like the one in this link, you need to look for this one. It might be on the circulating pump but 9.5 Ohms is wrong- are you sure the meter was on the correct scale?

http://www.ebay.com/itm/TPI-LT1-Coolant-Temp-Sensor-CTS-Wiring-Connector-/120606085882?pt=Motors_Car_Truck_Parts_Accessories&hash=item1c14aed2fa&vxp=mtr

Sensor-

http://www.ebay.com/itm/9364-1-Coolant-Temperature-Sensor-New-/200499599424?pt=Motors_Car_Truck_Parts_Accessories&hash=item2eaeb51840&vxp=mtr

nrojay
07-22-2013, 06:06 PM
yes same part and yes I had the wrong setting on meter
its measuring 3,000ohms but so is the old one, however I need to try the hot water to see if it changes it at all.

JimN
07-22-2013, 06:37 PM
yes same part and yes I had the wrong setting on meter
its measuring 3,000ohms but so is the old one, however I need to try the hot water to see if it changes it at all.

Then, test the old one first and return the new one if it doesn't read out of range.

Scan for codes. If need be, go to a Chevy dealer- you don't need to run it, just get the codes.

If your MAP sensor is at the side of the engine, below the throttle body, pull the vinyl tube off and see if any liquid comes out of the sensor.

nrojay
07-22-2013, 07:09 PM
ok I tested both sensors and yes they are testing the same

I took the vinyl black tube that attaches to the valve cover off at the throttle body and noticed nothing running out but very little oil inside the actual metal male nipple.

JimN
07-22-2013, 07:15 PM
ok I tested both sensors and yes they are testing the same

I took the vinyl black tube that attaches to the valve cover off at the throttle body and noticed nothing running out but very little oil inside the actual metal male nipple.

Your MAP sensor may be mounted to the intake manifold, so my recommendation might be wrong, but I stand by the one about scanning for codes before replacing any more parts.

nrojay
07-22-2013, 07:34 PM
Ok I snapped some pics of engine
98131

98132

98133

nrojay
07-22-2013, 07:54 PM
98135

98136

98137

JimN
07-22-2013, 08:43 PM
Ok I snapped some pics of engine
98131


The rectangle with GM on it is the MAP sensor- remove it (use PB Blaster on the screws) and inspect it. For that matter, unplug the harnesses from each sensor and make sure none of the terminals are corroded. While you're at it, disconnect the battery and check all of the ground points on the engine, measure from them to the battery (-) lug and make sure there's no more than .1 Ohm of resistance- .1 Ohms all that's allowable because any more will cause enough voltage drop to cause all kinds of problems. If you find any wires that feel stiffer at the end than the rest of the wire, make sure there's enough slack and replace the terminals that are needed. Use terminals that crimp on, solder them and if possible, use Heat N Seal terminals- these have glue that melts when they're heated and seals the wire. DO NOT skimp on the terminals- if regular crimp terminals are used, they will fail and Murphy's Law says it will happen at the worst possible time.

The rectangular piece you were holding is the diagnostic link, where the paper clip is inserted (or the scan tool). The paper clip inserts in terminals A and B.

nrojay
07-22-2013, 08:59 PM
I just took the Map sensor off is there any way to test this sensor
terminals on it look clean

nrojay
07-22-2013, 09:05 PM
Something else this weekend once when this starting happening I raised the cover and manually gave it throttle and it cleared up and ran out ok

JimN
07-22-2013, 09:37 PM
I just took the Map sensor off is there any way to test this sensor
terminals on it look clean

If you have a vacuum pump, you can connect a meter to the pins that correspond to the green and black wires and measure resistance as you increase the vacuum. It needs to vary. If it doesn't change and you hear the vacuum escape when you remove the tube, you should see code 33 or 34.

JimN
07-22-2013, 09:38 PM
Something else this weekend once when this starting happening I raised the cover and manually gave it throttle and it cleared up and ran out ok

Have you cleaned the flame arrester? If you look through it, you should see lots of light coming through.

nrojay
07-22-2013, 09:41 PM
yes the filter is clean
I cannot get any flashes at all using the paper clip method, im ASSumming the tansmission red light and the engine temp red light is deffective
I put the clip in terminals A and B

JimN
07-22-2013, 10:27 PM
yes the filter is clean
I cannot get any flashes at all using the paper clip method, im ASSumming the tansmission red light and the engine temp red light is deffective
I put the clip in terminals A and B

The high temp light may be a substitute for the normal check engine light but you can use an LED-type test light to sub for the dash light. IIRC, you would connect it to terminals E and F. I would call Indmar or MC to verify.

nrojay
07-27-2013, 02:09 PM
Took the boat to the local Orielys Auto parts store to hook up a diagnostic unit BUT they do not have a correct attachment to fit my Port on the ECM, I took it also to Another parts store and no luck either.

Any other ideas to pull a code or is there a way to reset it

JimN
07-27-2013, 05:00 PM
Took the boat to the local Orielys Auto parts store to hook up a diagnostic unit BUT they do not have a correct attachment to fit my Port on the ECM, I took it also to Another parts store and no luck either.

Any other ideas to pull a code or is there a way to reset it

Did you read my last post? Do that.

"Here's a way to do it using an LED instead of a test light.

Materials needed:

One 12volt resistor type LED light
One small paperclip cut in half


This home made code tool should work on all GM MEFI 1,2,3 or 4 marine EFI systems with the ten pin DLC (Data Link Connector).

How to hook it up:

1) Ignition key “OFF”
2) Remove the cap from the Data Link Connector (DLC)
3) Slide the LED into the female terminals of position E and F on the DLC, making sure that the positive side goes into terminal F and the negative side into terminal E
4) Turn the ignition key to the “ON” position (LED should come on)
5) Insert the half paperclip into terminals A and B – This puts the engine in “Service Mode” - (you will hear fuel pump come on, and code will begin to flash on the LED)
6) Read codes by observing LED flashs. If the self diagnostic system is working it will flash code 12 – one flash, pause, two flashes, long pause – it will repeat three times. If other codes are present they will flash in order of lowest to highest.

For more details on how to read codes, clear codes, what “Service Mode” is, how to set base timing, etc. refer to appropriate service manual.

I don’t recommend making and using this tool unless you are confident that you can do it correctly. Hooking it up incorrectly could damage the ECM."

I found this using google.

JimN
07-27-2013, 05:04 PM
yes the filter is clean
I cannot get any flashes at all using the paper clip method, im ASSumming the tansmission red light and the engine temp red light is defective
I put the clip in terminals A and B

Why would you assume anything without knowing the system? These were never meant for the boat owners to do the diagnostics- the authorized dealers had a diagnostic computer and this told us everything we needed without using the check engine light.

André
07-27-2013, 05:47 PM
Did you read my last post? Do that.

Here's a way to do it using an LED instead of a test light.

Materials needed:

One 12volt resistor type LED light
One small paperclip cut in half


This home made code tool should work on all GM MEFI 1,2,3 or 4 marine EFI systems with the ten pin DLC (Data Link Connector).

How to hook it up:

1) Ignition key “OFF”
2) Remove the cap from the Data Link Connector (DLC)
3) Slide the LED into the female terminals of position E and F on the DLC, making sure that the positive side goes into terminal F and the negative side into terminal E
4) Turn the ignition key to the “ON” position (LED should come on)
5) Insert the half paperclip into terminals A and B – This puts the engine in “Service Mode” - (you will hear fuel pump come on, and code will begin to flash on the LED)
6) Read codes by observing LED flashs. If the self diagnostic system is working it will flash code 12 – one flash, pause, two flashes, long pause – it will repeat three times. If other codes are present they will flash in order of lowest to highest.

For more details on how to read codes, clear codes, what “Service Mode” is, how to set base timing, etc. refer to appropriate service manual.

I don’t recommend making and using this tool unless you are confident that you can do it correctly. Hooking it up incorrectly could damage the ECM.

One day maybe,this will be in the FAQ or sticky somewhere ...:rolleyes:

JimN
07-27-2013, 06:52 PM
One day maybe,this will be in the FAQ or sticky somewhere ...:rolleyes:

I found that using Google.

nrojay
08-04-2013, 04:53 PM
Ok here is what has been done

No code was thrown on ECM

Replaced Plugs had incorrect went back stock
Replaced fuel pump it was wineing badly and I had already cleaned the screen maybe went to long before cleaning.
Replaced Fuel Filter
Pulled fuel cell and flushed and cleaned out along with the strainer in tank checked both fuel lines.

Took it out this weekend and it ROARED to life and ran out perfect
UNTIL we stopped to swim for a while when we went to start it up it was REALLY hard to crank
and then it would barely go almost sputering cutting out and then all of the sudden it Roared back to life. We ran for about 3 hours no problem but when we stopped for more than 45 minutes it would do the same symptom again.

I have read about a check valve in the fuel line on another post, mine does not have one I have followed the lines and had them off looking for it, others have said it was on the top of the tank where the fuel cutoff valve is located I have disasembled the complete fuel system and there is no ball and spring or check valve there.

Could this be the issue its bleeding down possibly ?

JimN
08-04-2013, 10:41 PM
Ok here is what has been done

No code was thrown on ECM

Replaced Plugs had incorrect went back stock
Replaced fuel pump it was wineing badly and I had already cleaned the screen maybe went to long before cleaning.
Replaced Fuel Filter
Pulled fuel cell and flushed and cleaned out along with the strainer in tank checked both fuel lines.

Took it out this weekend and it ROARED to life and ran out perfect
UNTIL we stopped to swim for a while when we went to start it up it was REALLY hard to crank
and then it would barely go almost sputering cutting out and then all of the sudden it Roared back to life. We ran for about 3 hours no problem but when we stopped for more than 45 minutes it would do the same symptom again.

I have read about a check valve in the fuel line on another post, mine does not have one I have followed the lines and had them off looking for it, others have said it was on the top of the tank where the fuel cutoff valve is located I have disasembled the complete fuel system and there is no ball and spring or check valve there.

Could this be the issue its bleeding down possibly ?

We were told to remove the ball and spring because it caused more problems than it helped. Next time, leave the engine cover open a bit to let it breath while it's not running to see if it's a heat soak issue. I would also measure the ECT-s resistance when it's hot- if it's too high, it's either not immersed in water or it's bad.

nrojay
08-04-2013, 11:44 PM
Forgive me but help me out with ECT

JimN
08-05-2013, 06:25 AM
Forgive me but help me out with ECT

Engine Coolant Temperature sensor. It tells the ECM that the engine is cool/cold (needs more fuel to achieve the correct fuel/air ratio) or warm/hot (needs less fuel).

Rather than open the engine cover if it won't start after sitting, open the throttle slightly and see if it starts more easily. If it does, do the resistance test on the temperature sensor. This is the one with two wires (one yellow, one black) and only reports to the ECM, not the temperature gauge.

nrojay
08-05-2013, 09:39 PM
ok cold the sensor is at 3k ohms
at 170 degrees it drops just below 1k ohms
I removed the sensor and used hot water heated by the stoveto bring up the temp for measuring

JimN
08-05-2013, 09:53 PM
ok cold the sensor is at 3k ohms
at 170 degrees it drops just below 1k ohms
I removed the sensor and used hot water heated by the stoveto bring up the temp for measuring

That's out of range when it's hot.
http://www.truckforum.org/forums/general-truck-forum/21957-testing-gm-coolant-temperature-sensors.html

What kind of thermostats do you have in the engine?

nrojay
08-05-2013, 10:57 PM
140 on front and 160 drilled on top from Mastercraft dealer

nrojay
08-07-2013, 06:09 PM
Does anyone have a part number
for an ECT sensor 95' LT1
Im thinking the shop put the wrong one in possibly

nrojay
08-11-2013, 01:10 AM
:D ALL is GREAT :D
I installed the new sensor and it ran like a champ !
I believe I had multiple problems

I changed:
1. fuel pump due to filter being so clogged I figured it was weak, even after cleaning it was making a bad sound
2. Spark plugs when I changed them out they were in very bad shape
3. Temp sensor
4. cleaned fuel cell and pickup
5. new fuel filter
6. 140 degree thermostat and 160 drilled thermostats
7. new water circulating pump old one was shot
Honestly the boat has never ran this good since I have owned it we had a great day on the water today!

thatsmrmastercraft
08-11-2013, 01:23 AM
:D ALL is GREAT :D
I installed the new sensor and it ran like a champ !
I believe I had multiple problems

I changed:
1. fuel pump due to filter being so clogged I figured it was weak, even after cleaning it was making a bad sound
2. Spark plugs when I changed them out they were in very bad shape
3. Temp sensor
4. cleaned fuel cell and pickup
5. new fuel filter
6. 140 degree thermostat and 160 drilled thermostats
7. new water circulating pump old one was shot
Honestly the boat has never ran this good since I have owned it we had a great day on the water today!

:woohoo::woohoo::woohoo:

thatsmrmastercraft
08-11-2013, 01:23 AM
:D ALL is GREAT :D
I installed the new sensor and it ran like a champ !
I believe I had multiple problems

I changed:
1. fuel pump due to filter being so clogged I figured it was weak, even after cleaning it was making a bad sound
2. Spark plugs when I changed them out they were in very bad shape
3. Temp sensor
4. cleaned fuel cell and pickup
5. new fuel filter
6. 140 degree thermostat and 160 drilled thermostats
7. new water circulating pump old one was shot
Honestly the boat has never ran this good since I have owned it we had a great day on the water today!

:woohoo::woohoo::woohoo: