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View Full Version : 1990 351 Bogs at 2800 rpm


hairlesshacker
10-11-2011, 05:35 PM
I have a 1990 TriStar 190 with the 351.

Recently it has started bogging down at WOT. Without a skier, it will only get up to about 3000rpm, and with a skier, it tops out at about 2800...
And when I turn a corner, the it drops down to about 2200, and sometimes won't do any more than that.. Usually it will gradually work back up to 2400-2600 if I keep it floored once I come out of the turn.

I am assuming it's a carb issue, and I've already got the rebuild kit from holley, just haven't gotten around to doing it yet.
(whenever I have spare time, I usually feel like skiing, not tinkering... then of course I get frustrated when it won't pull me right on slalom, and end up kneeboarding instead, since I don't need speed for that..)

Just wanted to ask here, is carb the most likely culprit? What else should I check? (I've checked fuel filters, but that's about it..)

Kevin 89MC
10-12-2011, 03:09 PM
Definitely sounds like a carb issue, possibly the secondaries are not opening up. Rebuild is fairly straightforward, mine went well. I would suggest you change both the fuel filter (by the fuel pump) and the water separator (in the bilge). I chased a stumble after my carb rebuild, both filters looked clean, but new ones cleaned up the issue.
Good luck,
Kevin

rjracin240
10-13-2011, 12:33 PM
Check your filter, fuel pressure, and fuel pickup in tank first before tearing into the carb. Definitely sounds like fuel flow limited.

j.mccreight@hotmail.com
10-13-2011, 01:39 PM
Check your filter, fuel pressure, and fuel pickup in tank first before tearing into the carb. Definitely sounds like fuel flow limited.

Did you get yours straightened out?

hairlesshacker
06-19-2012, 06:06 PM
So over the winter I've rebuilt my carb...
And it didn't help. The engine still bogs down when pulling a skier...
And sometimes is tough to start. (sometimes starts right up..) But generally runs rough...

Here's what I've done....
rebuilt carb with holley renew kit.
replaced fuel water separator filter.
replaced fuel filter on the fuel pump.
checked fuel pickup in tank, it looks good.. checked anti-siphon valve, it looks ok..
removed and checked fuel lines between tank and filter, and filter and pump. They look good.

(changed oil, replaced spark plugs)

Changed distributor from points to EI from skidim.. Checked/adjusted timing after changing it out. (still running stock coil though)

I replaced the fuel pump, but haven't had a chance to try it out yet.. but when I had the old one off, I didn't see anything obviously wrong (it sucked when I pumped) - so I'm not optimistic that it will help anything..

I guess it's time to buy a compression guage? not sure what else to check at this point.
maybe it's just time to take it to a real mechanic...

pkskier
06-19-2012, 06:46 PM
Replace the fuel lines the ethanol softens them up and the pump sucks and it collapses the line shutting down the fuel flow.

hairlesshacker
06-19-2012, 08:21 PM
The hoses feel pretty firm, but it can't hurt to replace them... I'll give it a shot.

thatsmrmastercraft
06-19-2012, 11:33 PM
So over the winter I've rebuilt my carb...
And it didn't help. The engine still bogs down when pulling a skier...
And sometimes is tough to start. (sometimes starts right up..) But generally runs rough...

Here's what I've done....
rebuilt carb with holley renew kit.
replaced fuel water separator filter.
replaced fuel filter on the fuel pump.
checked fuel pickup in tank, it looks good.. checked anti-siphon valve, it looks ok..
removed and checked fuel lines between tank and filter, and filter and pump. They look good.

(changed oil, replaced spark plugs)

Changed distributor from points to EI from skidim.. Checked/adjusted timing after changing it out. (still running stock coil though)

I replaced the fuel pump, but haven't had a chance to try it out yet.. but when I had the old one off, I didn't see anything obviously wrong (it sucked when I pumped) - so I'm not optimistic that it will help anything..

I guess it's time to buy a compression guage? not sure what else to check at this point.
maybe it's just time to take it to a real mechanic...

A compression check would certainly be in order. Are you getting any backfires through the carb when the engine bogs down?

hairlesshacker
06-20-2012, 01:55 AM
Yes, it did backfire once last time I had it out.

JaredOSU
06-20-2012, 02:45 AM
Definitely check the compression!!! Had this same problem. Is it running hot or rough? Mine ended up being a head gasket.

Philscbx
06-20-2012, 03:56 AM
Yes, it did backfire once last time I had it out.Usually a cough/backfire is a lean condition.

I'd run some Techron fuel injection cleaner - good stuff for carbs too.
How Old is the Fuel?
Smell test from sample - if uncertain - Test fresh sample & color.

* Live Spark test from the coil -
Needs to be sharp Blue - good 1/4"/3/8" jump to ground.
If orange - weak coil. 1/2" - 3/4" jump is possible.

* High Voltage insulation test -
Have good spray bottle of water w/drop of dish soap.
While running - fine mist wire by wire and then the coil tower.
Any Arcing - replace/upgrade.

Have compressed air to blow dry.
May need small silver 6x6 tarp to block out the sun.

* Fuel Pressure
Would be nice to see actual pressure of fuel - a simple test.
At carb feed line.

* Vacuum Leak Test -
At Idle - spray W-D at base of Carb to Manifold -
any random vacuum hose / to Distributor Vac Advance -
If engine Responds - There's the Leak.
Cause of Cough/Spitback/Backfire.

* Testing Accelerator pump -
Does it spray fuel in - Engine off.
Were floats tested inverted when carb was off to see correct setting level.
They can be corrected - while running.

* As for Compression Test -
Best if you call around to find a Leak-Down Tester.
Some Auto Supplies should have them to loan out.
Only need small compressor/tank to use it. Like Roofer style easy carry.

It can tell the whole story with pistons at TDC on compression/firing point.
Easily shows in real time the condition of Rings/Valves/HD Gasket.
This is standard for all piston aircraft, by law. If near a hanger - they can help.

* Timing Chain -
It's not uncommon for Fords to skip timing if chain is slack & still using nylon cam gear.
With Dis/Cap off - rotate engine back & forth 1/3 turn each way to see if rotor follows precisely.
Any Delay of rotor during move of crank by hand / breaker bar -
Chain & Gears need to be replaced. Very cheap fix.

You have most of the hard part done - these tests only sound tough.
Good Luck-

TRBenj
06-20-2012, 08:55 AM
Did you convert to EI before or after you started having problems?

Before digging in very far, I would at least go through the ignition and tune it up. Cap/rotor/wires, set the timing and verify the advance.

ctjahn
06-20-2012, 09:19 AM
Did you convert to EI before or after you started having problems?

Before digging in very far, I would at least go through the ignition and tune it up. Cap/rotor/wires, set the timing and verify the advance.

I am having a very similar problem AFTER changing to electronic...(Pertonix) although I am beginning to think it is is unrelated.... I hope to take some time and take apart the distributor this weekend. (and since it is time I am also doing plugs, wires, cap....while I am at it - if they arrive from skidim in time)

I have a feeling there is something going on deep in the distributor for mine. (broken spring and/or something isnt jiving)

EDIT: I have also emailed a request to Pertronix for input.

Pls keep me posted
Cj

TRBenj
06-20-2012, 11:05 AM
So the problem was present before swapping to the Pertronix? In that case, I would be a heck of a coincidence if you solved one problem and caused another that produced the same symptoms... but still possible (especially considering the Pertronix!).

I might be inclined to open up the distributor and see whats going on down in the base (weights/springs). I would also consider swapping back to points, at least for the short term, to help with troubleshooting.

Going through the rest of the ignition system is a good first step though. Once that is sorted through, I would move back to troubleshooting the fuel system.

hairlesshacker
06-20-2012, 12:58 PM
Symptoms for me started long before converting to ei..

PhilsCBX, thanks for all the tips! sounds like I'll need to take a few days off work to get through all the diagnostic tests...

hairlesshacker
06-20-2012, 06:36 PM
OK... so I went to harbor freight and bought a leak-down tester...

And I pulled the boat out, hooked the hose up to a bucket and started it up to get it up to temp so I could do the leak-down test on each cylinder...

That's when I realized.. I have no clue how to manually turn it.. :( Do I need to remove the raw water impeller? Or is there an easier way?

j.mccreight@hotmail.com
06-20-2012, 07:31 PM
OK... so I went to harbor freight and bought a leak-down tester...

And I pulled the boat out, hooked the hose up to a bucket and started it up to get it up to temp so I could do the leak-down test on each cylinder...

That's when I realized.. I have no clue how to manually turn it.. :( Do I need to remove the raw water impeller? Or is there an easier way?

You can try and use the alternator pulley nut if that doesn't work then yes you need to remove raw water pump to use the balancer bolt.

hairlesshacker
06-20-2012, 08:23 PM
yep, went ahead and took the raw water pump off, once I looked at it closer, I realized it was just a few bolts, easy enough, only took a few minutes...

followed the rotor around as I turned it.. and it turned right with the crank, so I guess that rules out timing chain issue..
this cheap-o leak-down tester I got only tests at 15 psi, but all the cylinders were pretty consistent around 25-30%, which doesn't seem too bad.

lhkrueger
06-20-2012, 09:11 PM
Check your fuel tank vent. A restricted vent will reduce flow when there is demand, but allow a slow recovery when there is not producing an intermittant problem. Might be collapsed or kinked.

j.mccreight@hotmail.com
06-20-2012, 09:46 PM
yep, went ahead and took the raw water pump off, once I looked at it closer, I realized it was just a few bolts, easy enough, only took a few minutes...

followed the rotor around as I turned it.. and it turned right with the crank, so I guess that rules out timing chain issue..
this cheap-o leak-down tester I got only tests at 15 psi, but all the cylinders were pretty consistent around 25-30%, which doesn't seem too bad.

25-30% not to bad but not great either, a good running engine will have about 15-20% leakage, idealy you want less than 10% and a 5% difference between all cylinders is acceptable. Could you hear where the air was escaping intake manifold exhaust manifold or pcv? However the test was not done properly, you need to do it at 80-100 psi regulated for accurate measurements and results.

hairlesshacker
06-20-2012, 11:38 PM
However the test was not done properly, you need to do it at 80-100 psi regulated for accurate measurements and results.

yeah, I should have read the online reviews for this meter before I bought it.. apparently there's a good hack for it if you replace the second guage, which I might look into doing.. As it is, the PSI only get to 15-20 before the second meter's at the "0" mark. Much higher than that pegs the second meter, which measures "percentage of leak" rather than PSI..

http://www.harborfreight.com/cylinder-leak-down-tester-94190.html

I probably just should have gotten a compression gauge for now, and not bothered with this. At the low PSI, the air didn't make much noise for telling where it was going... so I tried to hook the compressor directly to the hose at 80 psi, but my little compressor can barely keep up, and is too loud to hear over...

hairlesshacker
07-09-2012, 03:05 PM
Just wanted to post an update.. Finally got the boat out on the water this past weekend, and the problem has been resolved. No problem pulling a skier, plenty of power, no engine bog.

This is the first time I've had it out since replacing the fuel pump. And I also replaced the Coil.

I really don't know which made the difference, and I guess I don't care enough at this point to switch parts back to see...

It's still a little hard to start, although it will start every time if I floor it prior to cranking to give it that extra squirt of gas. I never really finished adjusting the carb after renewing it, so I'm assuming once I get that all adjusted I'll be good to go.

Thanks everyone for all your comments and suggestions.

thatsmrmastercraft
07-09-2012, 03:09 PM
Just wanted to post an update.. Finally got the boat out on the water this past weekend, and the problem has been resolved. No problem pulling a skier, plenty of power, no engine bog.

This is the first time I've had it out since replacing the fuel pump. And I also replaced the Coil.

I really don't know which made the difference, and I guess I don't care enough at this point to switch parts back to see...

It's still a little hard to start, although it will start every time if I floor it prior to cranking to give it that extra squirt of gas. I never really finished adjusting the carb after renewing it, so I'm assuming once I get that all adjusted I'll be good to go.

Thanks everyone for all your comments and suggestions.

Great to hear :toast:

Philscbx
07-09-2012, 11:55 PM
If you have a link to the leak down tester used - Id like to see - Thanks.
Like Jim stated - 80 psi is the norm. But these tools tell the whole story in one test which is nice.

As for a standard compression tool - it's not much help - several steps are needed for each cyl.
About as helpful as thumb over spark plug hole - gives enough info.
Typical engine needs 90 psi to fire off.

Great that he's up & Running.

hairlesshacker
07-10-2012, 05:37 PM
Link to the leak-down tester is in prior post.. http://www.harborfreight.com/cylinder-leak-down-tester-94190.html

There's notes in the comments/reviews about it's problem. Rather than the second guage measuring PSI, it measures "percentage loss", so you have to start with it reading 100.. well, 15 psi reads 100, and anything higher pegs the meter. Others have fixed it by replacing this "reverse" meter with a normal 0-100 psi guage, so it functions like a normal leak-down tester and can operate at higher psi.

Playing hookie Prostar 190
07-12-2012, 10:04 AM
check the spark plug wires routing/ firing order . if two wires are crossed it will run that way.

Philscbx
07-12-2012, 06:29 PM
check the spark plug wires routing/ firing order . if two wires are crossed it will run that way.Not really - as it's running pull a wire to see if power is the same or drops - if no change it's crossed.
In effect - two dead cylinders.