got another problem for you guys

if you have read my previous threads you know i have replaced both my fuel pumps recently and it was driving great until a month or so ago.

seems to be a erratic problem of accelerating poorly, by this i mean i can give it a slight push on the pedal to go but any type of quick acceleration cause the car to bog down, to solve this i shut the car off and turn the key to accessory until i hear the fuel pump under the car engage(it is a distinct but not loud sound) sometimes it may take 5 or 6 key turns but after i hear the sound and start the car up it drives just fine.

i am think something electronic like the fuel pump relay or even just a bad connection to the fuel pump itself as i was not very fond of the wiring connections on the generic fuel pump.

any suggestions or thoughts are appreciated

 

Others will reply no doubt pretty soon with actual experience in this topic, but from what I understand the fuel pump relay often goes bad. if you can test that, it is generally somewhat easier to get to than the fuel pump itself. Then if you can rule that out, You move to the fuel pump.

In my experience with electronics, that sounds like a problem with your solenoid in your fuel pump relay, though. Admittedly, my experience in electronics is in fire alarms & security systems, but if I were a betting man I would put my money on the relay. Which also encompasses one other thing--check your grounds. Many intermittent electrical problems are caused because the system isn't grounding very well.

 

the fuel pump shouldn't be activating at all in I (accessory)... the ECU is only powered in II (run) or III (start), and may turn the pumps on for a second or so when the key is first turned to II (not all do this, I think it depends on the ECU firmware revision).

 

yes i may end up replacing the relay as it not that expensive also having problems with my over drive relay not disengaging but that is another problem.

and pierce the fuel does only activate for about a second in I (accessory) but the problem is it doesn't always engage and that is when i seem to experience the problem. which is why i continue to turn the key until the fuel pump can be heard for the second or two and then the car drives fine.

 

this is a 1991 740?

is it Bosch LH2.4 or Regina, and is it a B230FT turbo or B230F plain ?

I'm double checking the factory "greenbook" schematics for a 1991 740/940, and same as every other 740/940 I've seen or looked at the prints for, LH2.4 only powers the ECU and fuel pumps in key positions II and III (start), they should be disconnected in I auxiliary.

Regina is wired the same. so if your pumps are spinning for a second in I, there's a wiring problem, or something is seriously whack.. Are your dashboard indicator lights also lighting up in I ? They shouldn't be, they should only light in II.

 

yes a 91 740 i believe it is the bosch and it is a a turbo so b230ft.

and i believe when the key is turned it is building up pressure which is why the pump engages briefly. was not aware this is uncommon in cars? and yes the dash lights come up, technically i think it would be when the key is on run but not actually having started the car.

sorry for the bad explanation earlier.