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87 TBI stall problem

I have a 1987 G-20 Van with a 5.7 TBI engine. Recently, it's began to stall when you make a right hand turn. It seems to do this more when the engine is warm, but that's not true all the time.

The one thing it DOES do consistantly: Restarting the engine always requires the key to be turned off before it restarts. Leaving the key in the on-position, and cranking it, it won't start. Turn the van off, and then restarting it is no problem, and it starts within a few seconds.

This leads me to believe that it's a relay problem, or a problem with the ECM. The engine produces no fault codes before, or during the event, and everything the computer displays looks OK before the event, as well as after.

Any help would be greatly appreciated.

Thanks! Lee snipped-for-privacy@nospam.annasart.com (just remove the nospam. from the address... Thanks!)

Reply to
Sorcerer
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Well, let's see.. the oil is fine, and full. It averages around midway or better on the gauge, so there could be a failure in the oil sensor switch. I haven't figured out where the fuel pump relay is, since that was my thought as well. Do you have any recommendations about where to look for it? My thought was that the relay is unlatching while driving (loose connection), with nothing to re-energize it.

Lastly, the problem doesn't change with the amount of fuel available, though, when turning the switch on and listening to the pump run, I don't hear any change in pitch or speed while it's in it's priming stage (about

20 seconds). Is it possible that the pump is wearing out? I got under it this evening to check on the possibility of dropping the tank to check on it, and some moron before me welded a frame mounted trailer hitch in place, and removing the fuel tank will involve cutting torches to get the hitch dropped before I can drop the tank, which I don't have access to currently.. Geez.. Some people, huh?

After working on it for several hours today, I found that after it is hot, and hot outside (everyday here in Phoenix) I can duplicate the failure. It seems not to be related to the right hand turn (which I had problems understanding,) but a rapid decrease in engine RPM such as letting off the accelerator as you would around a sharp corner, and then accelerating after the corner. I was able to finally duplicate the stall by setting in my driveway, punching it, quickly letting off the gas, and having it stall.

This seems more vacuum or fuel related, but the vacuum lines seem OK, so we're back to fuel/fuel pump.

Reply to
Sorcerer

I think it's time to bring it in an have it hooked up to a scope. There are a few more possibilities that spring to mind based on your new info. Faulty TPS, MAP sensor, fuel pressure problem, etc. Without the right diagnostic tools, you will probably throw several parts at it before you hit the mark. If you want to test the TPS, unplug the wiring and put an ohm meter across the terminals. There are 2 different style TPS for that year, so I don't which type connector you have. But try any two terminals and see if the ohms change while you move the throttle. If they don't, move one of the wires to the other terminal. look for any irregularities, such as the needle bouncing (yes, an analog meter is best for this). If it jitters around idle or just off idle, that's probably it. The needle should move very smoothly across the range. Check the vacuum hose to the map sensor. It comes out the base of the throttle body. The sensor on the van, I believe, is located inside edge of valve cover, passenger side, adjacent to Throttle body, with the hose going down to the rear base of TB. It has a three wire connector on it, and is often on the same plate as the Spark control module. If you don't find anything there, let a shop look at it, or someone with a fuel pressure tester.

Reply to
John Alt

Well, after a good suggestion from the another group, I checked the oil pressure fuel cutoff switch. Turns out it's killing the fuel pump at 25-30 psi, instead of 4, like it's suppose to.

Replacing that has solved the problem.

Thanks everyone! Lee

Reply to
Sorcerer

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