• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

92 740T will start fine once, then sputters out and will not restart and stay running

baddecisionsmadedaily

baddecisionsmadedaily

Member
Joined
Feb 21, 2024
Location
Portland, OR
Recently did a radiator on my car, and after the radiator the car had felt a little sluggish off of the line for a while. Then last week, was driving out of the neighborhood and suddenly the car died right on the spot. Wouldn't restart for the life of me so I went back home and got the 2nd vehicle, jumped the car and got it back home. A few days later go to drive it and it starts right up, but the moment I go into reverse it bogs out and dies, and then wont restart easily, and when it did start, it would barely fire. Come back the next day and it does the same thing. Starts, runs fine, goes to move and dies and then will not happily restart. I can smell fuel and I hear the pump prime, I checked all my plugs to make sure they are all firing, and I have checked the maf to make sure it is working. I know I have had some blowback, but I dont see how that would let it start totally normal one time and then kill itself under load. Any ideas? Was thinking maybe a hose is collapsing internally?
 
Really scratching my head with this one, and any help is greatly appreciated. Got a little one on the way and trying to keep wife from making me toss the brick, but with it not running and not having much of a clue what is causing it, im in a losing battle.
 
240 240 said:
why did you change the radiator?

did your car overheat? do a compression test
Click to expand...
Car did overheat slightly, but had been running and driving for a few weeks before this issue popped up. I know it had pretty low compression beforehand, but more so confused as to why it will start up fine when it sits for a day or so, and then the moment I put it gear and try to move, it dies and then struggles hard to restart.
 
Most sensors and such have been replaced. New alternator, new starter, new ignition, new cps, most of the vacuum lines have been replaced, I verified turbo is spinning freely, and have confirmed it will start up after the mentioned issue if it sits overnight.
 
I would suspect a bad connection at the radio suppression relay, or, the relay itself if bad. The same could be said for the fuel pump relay. The fuel pump relay is actually 2 relays in one. One relay supplies the fuel pumps with power. The other turns on the injectors etc.
 
baddecisionsmadedaily said:
Really scratching my head with this one, and any help is greatly appreciated. Got a little one on the way and trying to keep wife from making me toss the brick, but with it not running and not having much of a clue what is causing it, im in a losing battle.
Click to expand...
This symptom is a typical one with a bad fuel pressure regulator. It might not be leaking internally. The diaphragm goes bad and won't let it regulate the pressure. The pressure goes too high and floods the engine. A fuel pressure test will show if it's the cause. As twomanyturbos says it could also be the RSR.
 
dl242gt said:
This symptom is a typical one with a bad fuel pressure regulator. It might not be leaking internally. The diaphragm goes bad and won't let it regulate the pressure. The pressure goes too high and floods the engine. A fuel pressure test will show if it's the cause. As twomanyturbos says it could also be the RSR.
Click to expand...
Or, if the diaphragm in the fuel pressure regulator is ruptured fuel will be running up the vacuum line straight into the intake manifold. It will literally drown the engine.
 
Found a small cut hiding under the zip tie to the FPR when I pulled the line to check for failed diaphragm. Cut line shorter and reattached, haven't test driven but the blip in the throttle seems to be gone, and it hasn't died under load as of yet.
 
I think that will need to be next, as after getting front hose reattached the rear hose started leaking. Wondering if maybe for is clogged vs being ripped. Even then, vacuum is sitting at -10 when I feel like before all this it would sit closer to -20ish at idle. Was able to move under its own power around the parking lot, but when I give it any gas, it bogs out and wont restart until it sits for a few hours.
 
baddecisionsmadedaily said:
I think that will need to be next, as after getting front hose reattached the rear hose started leaking. Wondering if maybe for is clogged vs being ripped. Even then, vacuum is sitting at -10 when I feel like before all this it would sit closer to -20ish at idle. Was able to move under its own power around the parking lot, but when I give it any gas, it bogs out and wont restart until it sits for a few hours.
Click to expand...
Vacuum sitting at 10in is usually an air leak. I had that type of reading when the compressor bypass valve failed. So more checking on that ol beast.
 
baddecisionsmadedaily said:
I think that will need to be next, as after getting front hose reattached the rear hose started leaking. Wondering if maybe for is clogged vs being ripped. Even then, vacuum is sitting at -10 when I feel like before all this it would sit closer to -20ish at idle. Was able to move under its own power around the parking lot, but when I give it any gas, it bogs out and wont restart until it sits for a few hours.
Click to expand...

The car should idle fine with the FPR vac hose in your pocket. (disconnected)


Keep trying. Massive airleak?

If it is falling on its face when you accelerate....I am gonna guess your shit is hella lean
 
Last edited:
The intank fuel system is known for having problems on these cars. The pump fails, transfer hoses tear, rust/debris are known to be an issue at this age too. Finding fittings to check fuel pressure isn't easy. I usually update to the 1992+ fuel rail and have an IPD 90 degree fuel pressure tester.

If it runs and won't accelerate, that reeks of lack of fuel volume/fuel pressure/or extremely lean.

As mentioned, check the wiring for the fuel injector (RSR) relay. It is on the strut tower. One is for the front fan and is the same relay. The wiring degrades and will cause a no start/stall.
 
Last edited:
ZVOLV said:
The intank fuel system is known for having problems on these cars. The pump fails, transfer hoses tear, rust/debris are known to be an issue at this age too. Finding fittings to check fuel pressure isn't easy. I usually update to the 1992+ fuel rail and have an IPD 90 degree fuel pressure tester.

If it runs and won't accelerate, that reeks of lack of fuel volume/fuel pressure/or extremely lean.

As mentioned, check the wiring for the fuel injector (RSR) relay. It is on the strut tower. One is for the front fan and is the same relay. The wiring degrades and will cause a no start/stall.
Click to expand...
The thing that gets me is it seems more like its getting too much gas. It will start up and run, but if I put any load on it it will bog and then nothing I do will get it to restart on all 4 cylinders. Just confuses me on if it is a lean issue, why will it not restart until it sits for a few hours? Been trying to get out and mess with it, but Portland rain and no garage/carport make for difficult times checking things.
 
You must log in or register to reply here.
Back
Top