1993 Fleetwood hot start problem

[John D. Hague]

Two questions . . .

1. When I disconnect the purge line from the cannister to the TBI unit, do I need to plug that line in any way for drivability?

2. The factory Manual for the car says " The fuel meter cover includes a bleed orifice that relieves system fuel pressure when the engine is turned "OFF". My fuel pressure is within spec (10-12 psi) when the car s running but drops pretty quickly when the engine is turned off. I assumed that this was due to that bleed orifice. You indicated that the pressure should stay up for quite a while which I understand is the usual case for most cars. Is the design of this car with this bleed orifice different? Is it then OK if the pressure drops off?

John

[N0DIH]

No, it is on the inlet side, so it won't hurt anything. It has a very small suction there, like 1psi or so.

You can also try loosening gas cap to relieve tank pressure. That was the "fix" for the LT1 cars with this issue until you fixed the bent/crimped hose underneath the canister.

It shouldn't bleed off for a few min, if not 10-15 min. Anyone got a FSM with the test proceedure? I can look at my 85 Cadillac FSM at home and see what the HT4100 spec'd. Should be the same.

It isn't ok if it goes into the engine ( via the vacuum line ). do you have a vacuum pump? Check the fuel pressure regulator for its ability to hold vacuum. Check for fuel on the vacuum hose, if there is, replace it ASAP, that is the problem.

Once below the 10-12 psi, it should hold 100% of the fuel, eventually it will bleed out back through the pump, but it should hold for a while.

My port injected cars it holds for a long time, an hour or so last time I checked.

[John D. Hague]

I realize that this may be a stupid question . . . . I do have a hand-held vacuum pump but I can't figure out where the vacuum line at the fuel pressure regulator is that you are talking about. That regulator is down in the middle of the TBI assembly and it isn't clear to me how I would test it.

Incidentally, I deeply appreciate the patience that you have with me.

John

[N0DIH]

I don't have a TBI powered car/truck, so I can't help. Anyone here have one that can help??

No problem at all! I would rather take the time to see you figure it out vs paying a shop and spending a ton of cash. You'll be happier all the way around. Maybe not as fast as a shop, but you learn something for sure, even if we don't know the answer, you still learned something....

Always remember, you need fuel and spark to make an engine run, and proper amount of both. If you don't have one or the other, then you won't have it running. When it does start after is gives you the trouble, does it black smoke at all?

[John D. Hague]

No black smoke that I have observed. It just runs in a fuel-starved kind of mode in which it sputters for about 3-5 seconds and then smooths out and runs fine.

This never happens when the temperature is below about 80 degrees regardless of how far I drive the car. And now the temperature in Indianapolis is cool enough that I can't duplicate the failure mode. That complicates my analysis efforts.

[N0DIH]

Yup, it does. But if it is fuel related, it likely will get worse.

Check around fullsizechevy.com for the same failure mode, there were a LOT of TBI 350's in the trucks. Lurk around impalassforum.com too, again, lots of TBI's in the 90-93 B/D Body cars too. Even the L03 is similar (the 305 version). The 454 (L19) is similar as well, so don't discount the tips on those engines, they are all a very similar system. Try http://www.thirdgen.org/techboard/tbi/ too, they had TBI's too (L05's even!)

If you can datalog, you can definitely see more too. It is more advanced thing to do, (not sure how technical you get), it costs around $50 to get into it. Have to see for sure if the L05 can be datalogged.

ECM's for these cars are cheap, so DO NOT get into spending much on them. If you pull yours out (not sure where it is in that car, the LT1 it is behind the left front headlight under the air cleaner) and send me the PN I can look around. You can check my first place, car-part.com. I don't think that is it, so do rush off to replace parts. ECM's are temp sensitive like this at all, I don't think that is it at all. I don't like tossing parts at a problem that isn't fully understood.

It strikes me as fuel related, probably the pump or the regulator. Most likely the regulator.

Try some reading here: http://www.thirdgen.org/techboard/tb...check-out.html

Look down at fuel pressure regulator....

[N0DIH]

http://www.thirdgen.org/techboard/tb...ml#post3534742