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ride
08-09-2007, 06:47 PM
My '95 LT1's acting up and not sure why. I'm relatively sure it's a fuel-line issue, but need somebody to double/triple check my logic if there's anything else I should be looking at.

Issue:
While on the 1st day of a 4-day trip at the very remote location of Lake Powell the engine started acting like it would "miss". Really gradual at first, almost like there may be mosture in my fuel but got worse with each day to the point that when trailering the last day, it began to stall.

Observations:
- the "miss" started out more like a sleight stumble, but RPM drop would increase as it got worse (lost 1,k +rpm with every miss)
-miss was steady, almost timed.
-Engine temp was running a little high (175) but dealer said not to worry as lake water temp is like 83 degrees.
-Hadn't used boat much last season while tied up with "projects" thus bad/old fuel and/or condensation were suspects
-Loud whine coming from fuel pump

Attempted corrections (to no avail):
-Added Heet in case of bad fuel/condensation
-changed post-pump filter (but did't have a spare for the pre-pump side)
-pulled and crudely blew out the pre-pump filter
-replaced fuel pump (dealer overnighted to the nearest marina @$350:mad: ) since the old one was so loud and had to be the problem (yeah, right).
-used a water-toy inflator to back-flush both the fuel line from pump inlet and return line, which seemed to help for about 2 min. and then prob returned.
-Checked spark in all plugs- all ok.

Now that I'm home, I'm gearing up to blast the problem out this weekend.
To do list:
-Drain all fuel from tank and wipe out any sediment I find.
-Clean out inlet screen on pickup tube
-Replace both pre-pump and aft-pump fuel filters.
-blow out tank vent tube
-find fuel inlet screen near pump and clean out. (where is that exactly?!)
-Replace with nice, shiny, clean gas and repressure line.
-Pick up fuel line tester and test pressure at schrader valve at idle, half, and WOT.

Is there anything else for me to think about doing while I've got it all apart? Again, to me it seems to be fuel, but should I be considering anything else? Intermittently bad coil pair perhaps? ECM rev governor due to overheat? Air intake sensor? Injectors?

tommcat
08-10-2007, 04:24 PM
i wouldnt do anything until you verify fuel pressure while it's acting up

School Skier
08-10-2007, 05:08 PM
I'm going through an issue with fuel line or something related and we have not found out much yet.
Good Luck!

chevy08bud
08-10-2007, 05:46 PM
ride- The screen that you are looking for is in the fitting on the bottom (inlet side) of the pump. From what I've found out through researching another problem, a loud whine coming from the pump on that engine is sometimes an indicator of this screen being blocked. When you fill back up with fuel and are all ready to go, you may have to disconnect the fuel line from the tank and pour gas into that line until you hear gas spilling back into the tank. This will fill both your inlet and return hoses with gas and you will be able to get a prime on your pump this way. May not have to, but this was the root of the problem that I had. Once everything is back together, and fuel is in the lines, turn the key to the run position, but don't turn over the engine. You should hear the pump come on for approx. 2 sec. and then turn off. Do this a handful of times. You should hear a change in pitch as you get more fuel and pressure built up. After that, using a rag and something to depress the schraeder valve, check to see if you have fuel at the valve. If you do, then hook the water up to it and fire it up. If the fuel seems to be ok, then you are looking at either an intermittent coil, or an ignition module. The ignition module on these I believe sits under all of the coils. Hope this helps.

JimN
08-10-2007, 05:57 PM
Loud whine isn't a good thing- make sure the fuel pickup is clear. Best thing to do is remove the fuel line from the pump, use a container to collect what gas is in the line from the tank forward and see if there's any restriction in the line. That means blowing from the pickup to the pump. Best way to do this is by attaching a fresh piece of hose to a hose barb fitting, screw that into the same piece the pickup is threaded into and just blow into it. If there's significant blockage, you'll know it and won't need a gauge. If there's a blockage, start eliminating the possibilities by bypassing the anti-siphon valve and repeating. It is possible to have a bad fuel line, too. Your anti-siphon may be sticking, too. That means it should be replaced- it's not expensive enough to try rebuilding it.

One issue I have with the diagnostics is that you didn't use the boat much last year and if the impeller stayed in the raw water pump, that could explain the higher than normal temperature and the RPM drop. An impeller that stays in a pump develops "set" and will never pump as well as a fresh one. You also don't include impeller replacement in your list. Replace it. The fact that you didn't use the boat much means nothing. It's from two years ago and needs to be replaced.

pilot02
08-10-2007, 06:06 PM
Spend 15 or 20 bucks on a fuel pressure tester at your local auto parts store and check the pressures engine off and while running. We just went through this exact thing with a friends 96 LT1. Started out stumbling randomly so we switched to my boat and the LT1 died completely on the trip back to the dock and I had to tow them in. Checked fuel pressures and after repeated cycles could only get it to 24psi. Pressure would drop to 5-10 while cranking and at that point the engine would not fire. Checked both filter's and the screen and ended up replacing both external filters and the pump. Runs fine now.

pilot02
08-10-2007, 06:06 PM
Ooops double post...

ride
08-10-2007, 08:16 PM
Thanks for the input and stuff to be checking while I've got it apart. Hey JimN, I should've listed it, but I did check the impeller (as well as thermostats for sticking) and replaced all since I carry a spare (not my first rodeo). Really didn't have much effect on my temp reading tho, thus prompting the call to my dealer to be sure it'd run at that temp. Where am I looking to find my anti-siphon valve? Is that different that my tank vent line?

ride
08-10-2007, 08:27 PM
[QUOTE=chevy08bud]ride- The screen that you are looking for is in the fitting on the bottom (inlet side) of the pump. From what I've found out through researching another problem, a loud whine coming from the pump on that engine is sometimes an indicator of this screen being blocked.QUOTE]
Chevy08bud,
Thanks for that. I swear that thing runs and hides in a new spot everytime I think to check it. Out of curiosity, when I swapped out my fuel pump, it wouldn't have fallen out or was inside the pump inlet fitting on the pump body itself? I really wasn't watching for it when I swapped that pump out. Guess if its gone, it must not be the problem I'm having, right?

JimN
08-10-2007, 08:50 PM
The anti-siphon is for keeping the gas from draining if the fuel line is cut. If you look at the plate on the tank where the fuel line attaches and the whole fuel line assembly, it goes from the tank, up through the pickup tube, makes a right angle turn, goes through the anti-siphon, there may be a shut-off valve, fuel filter, fuel filter, then to the pump.

The vent keeps the tank from pressurizing from heat expansion and having negative pressure due to fuel use. If the vent or its tube is clogged, the fuel won't be drawn to the pump the way it should.

If the boat runs badly and loosening or removing the gas cap fixes the problem, it's usually a clogged vent/line.

Jorski
08-13-2007, 02:12 PM
Just a note: if you are looking for the screen everyone keeps referring to, you have to remove the bronze fitting that attaches to the fuel line, other wise you can't see it.

The screen was the culprit for me several times over the years.

ride
08-13-2007, 06:39 PM
Just a note: if you are looking for the screen everyone keeps referring to, you have to remove the bronze fitting that attaches to the fuel line, other wise you can't see it.

The screen was the culprit for me several times over the years.
Thanks for the specifics. Just got my pkg. of replacement goodies from Skidim today so I'll start my tear-down tonight and will post my findings later in the week once its all back together.

ride
08-13-2007, 07:23 PM
The anti-siphon is for keeping the gas from draining if the fuel line is cut. If you look at the plate on the tank where the fuel line attaches and the whole fuel line assembly, it goes from the tank, up through the pickup tube, makes a right angle turn, goes through the anti-siphon, there may be a shut-off valve, fuel filter, fuel filter, then to the pump.

Still confused on the antisiphon. Is it a seperate fitting? From the assembly plate, I'm seeing the 90 degree elbow fitting that immed. attaches to the shut-off/ball valve, then attaches to fuel line, then in-line filter, then pump, then high pressure filter just before my injector bank/pressure check fitting. JimN, what am I missing?

André
08-13-2007, 10:14 PM
Still confused on the antisiphon. Is it a seperate fitting? From the assembly plate, I'm seeing the 90 degree elbow fitting that immed. attaches to the shut-off/ball valve, then attaches to fuel line, then in-line filter, then pump, then high pressure filter just before my injector bank/pressure check fitting. JimN, what am I missing?
http://www.tmcowners.com/teamtalk/showthread.php?t=17776&page=2

Check here for your answer.Don't hurt to reread the whole thread...:)

ride
08-15-2007, 03:27 PM
Thanks Andre. Only problem is that my barb is clean (e.g. I see nothing in it at all, no spring-loaded ball bearing or anything else for that matter. Just the ball-valve for the shut off. Is that how its supposed to be?

ride
08-15-2007, 03:39 PM
The anti-siphon is in the barb where the fuel line attaches to the right angle fitting. It's just a spring-loaded ball bearing but as long as it keeps gas from siphoning out, it works. Problem is, with the pump drawing gas from the tank at the rear of the boat, the valve can actually cause other issues...

JimN- This is from that other thread. If I'm not seeing anything in my barb end of my shutoff valve, is that a bad thing, or am I just not seeing it? I can't imagine it was left out upon assembly. Reagardless, right now the fuel pickup and line are clean and obstruction-free to that point. If in fact I don't have an anti-siphon, is that something I'll want to remedy with my dealer's parts dept for it to run optimally?
Mights well do it now while I have it all apart....

chevy08bud
08-15-2007, 04:23 PM
You probably don't have an anti siphon valve. I have a 94 and didn't have an anti siphon valve, just the shut-off valve that you have. It won't hinder performance if you don't have one, so I'd just keep it like it is.

ride
08-20-2007, 01:26 PM
Just to report, after having followed the steps everyone (esp. JimN) helped me out with in this thread and in previous threads, upon lake-testing this weekend, all is back to normal. Everything fired right up and ran smoothly, fuel pressure tested right near 40 PSI in all positions and no whine from my fuel pump. Something to note should anyone have the same issues and perform the same checks, MAKE SURE to pressure test your fuel line BEFORE heading to the lake once everything's put back together. I found a relatively insignificant leak on a fitting attached to my fuel pump's non-pressured return line that I'm stoked I caught before leaving. NAPA stocked the fitting and cost $1.02. Small price for the peace of mind. Only issue I noticed at all was a sleight rise in my oil PSI, running 60 at 2,k rpm (might have been there before), but gets up there at WOT. I'll see what I can find our about that in previous posts but feel free chime in. Thanks for all the input.