fuel pump or relay? or both?

1990 744Ti

So last night I was coming home and while parking on the street my car decided to stall out on me and didn't want to restart. Every now and then it would restart for a second, then idle like crap and die out again. As I was pretty much in the spot, I just left it and came back about 1/2 hour later to recheck it. It started, but had a very poor idle and didn't want to run well, if I gave it any gas it would bog down and stall. Checked AMM, swapped out radio suppression relays and still didn't want to run well. I waited about an hour and checked again, started up fine and ran fine.

This morning on my way to work car started and ran ok, but then just stalled in the middle of an intersection (bogged down and if I gave it any gas it would just bog more). Pushed it back down the road to a street spot and let it cool down again. Would not restart. Even after 2 hours of letting it cool down. Big white fuse relay over toward the right of the fuse panel clicks every time I turn the key to position II/ACC. Car will crank and crank but just won't turn over. I can't hear the pump turning to when I turn the key over to position II/ACC, which normally I can. Could this still be a relay problem (or a wiring problem), or do pumps wear out like this? I've never had a pump wear out on me, so I have no idea what to expect.

Any help is appreciated! Thanks

Could be the pump, have you checked to see if the fuel pressure is correct at the fuel rail when you go to start the car?

Another thing to look at is the fuel pressure regulator. If you remove the vacuum line from it and smell gas in the line, it is bad.

But will the FPR cause the car to just suddenly not start at all. I can't hear the pump come on at all, and haven't checked to see if there is any fuel at the rail when I'm cranking it over.

As I crank the car, the tachometer jumps and falls as it should when cranking over the car, but it just won't turn over

bump

Fuel pumps and relays tend to go bad so you just have to test all of your components.

Check for fuel at the rail this is crucial dude.

There is no way to answer your questions for you without you doing some work.

Start testing components.

So... spark is fine at all plugs...

Fuel running well up to the rail, but nothing coming out of the injectors. Could this be the resistor pack? or something else I'm totally missing.

Thanks

Flyingbrick90 said:

So... spark is fine at all plugs...

Fuel running well up to the rail, but nothing coming out of the injectors. Could this be the resistor pack? or something else I'm totally missing.

Thanks

Click to expand...

See if you are getting power to the injectors. I just went through this. It was a Bad CPU.

no power to the injectors!

Where is the CPU and how much am I looking at spending to fix this?

aaah.

Flyingbrick90 said:

no power to the injectors!

Where is the CPU and how much am I looking at spending to fix this?

aaah.

Click to expand...

I would double check the basics first.
the units are in the pass foot well and under drivers side dash.
I would check voltage to the RSR and see if it is getting there.
cpu's are arround $85 -$120 for both @ a junkyard.

As I was told take a spare injector hook it up and have somone crank the car to see if it pulses.

RSR? What does it stand for and where would it be located? - radio suppression relay.... already switched it out and to no avail, but it was a JY unit so it too may have been bad. what about the fuel injector resistor located on the driver's side fender? could that be the culprit for all 4 injectors not pulsing?

which unit is most likely the culprit, as I have no 740T's of the 1990+ vintage in the JY near my home and no real time to go elsewhere. Therefore, I will likely be trying to buy one from fleabay or from some fine folks from here!

Flyingbrick90 said:

RSR? What does it stand for and where would it be located? - radio suppression relay.... already switched it out and to no avail, but it was a JY unit so it too may have been bad. what about the fuel injector resistor located on the driver's side fender? could that be the culprit for all 4 injectors not pulsing?

which unit is most likely the culprit, as I have no 740T's of the 1990+ vintage in the JY near my home and no real time to go elsewhere. Therefore, I will likely be trying to buy one from fleabay or from some fine folks from here!

Click to expand...

Take a look At this for the RSR.
http://www.brickboard.com/FAQ/700-900/EngineFuelinjection.htm#Radio_Suppression_Relay

I did swap them (since I don't know which is for fan and which is for engine) - one on coolant reservoir and one behind power-steering reservoir, however that being said, it was to relays that I got out of the junkyard, so who knows if they were any good. I'll try swapping them again today and see if that could be the problem.

Also, could this be the crank position sensor, or would I not have spark if that were the case?

Thanks again!

could be crank position sensor. Read up on the brickboard FAQ link that volvos3 posted, a ton of good info though. Sounds alot like the same symptoms my buddy had when the ECU on his 240 went bad. I'm sure someone on the board can sell you a spare for cheap.

Whats the updated status? I doubt you have a bunch of bad relays.
I have a 0 280 000 560 That I wouldnt mind sending you free as long as its LH 2.4.

Swapped out the resistor pack this evening when I got home from work and she fired right up like nobody's business.

Thanks so much for all the help and the offer on sending the ECU along. You all rock!
(Though I may need to take you up on the offer of the ECU in the future (as mine is a 560) and I certainly don't have 415 bones to shell out to FCP if it goes bad!
Thanks again

Really! That is Awesome! Sure no problem but now it is for sale! LOL! Shipping cost about $90.00.. Ha Ha. Jk if you want a spare pm me your addy and I'll send it to you I have no use for it.

Interesting, I've never heard of a resistor pack going bad. Maybe it was just a bad connection?

Nah... Swapped it back and forth a few times because I didn't think it was possible, but power ended at the resistor pack, and car only starts with the replacement. Who knows...volvos3, I will pm you tomorrow or Saturday, and plan to pay well for the shipping charges!

Thanks again guys