I am stumped and in need of some advice and suggestions. My 85 740 Turbo sputters and stutters upon acceleration. I took it in for diagnosis and the opinon was that it was the fuel pump since it was only putting out 17psi and really noisy. The in-tank pump worked fine. I am the second owner and the fuel pump had been replace before to a new Bosch one. So, I bought a good used one and a new fuel filter and changed the previous new one for the used one. Ran fine for a while then the used fuel pump quit, with a lot of noise before its demise. So, went out and bought another good used one that looked nearly new out of a wrecked turbo car and installed that one. Ran fine then it quit too, with a lot of noise before its demise. So, I changed the fuel pressure regulator and got another one. But this one started off the bat with a lot of noise, although now I don't have the sputter ect., but it seems only a matter of time before this pump fails. I checked the fuel pump relay and it was really hot.

I am perplexed as to why so many pumps that were good have failed on my car. The in-tank pump works fine. Could there be some electrical problem and if so, how do I check it. Could there be a blockage some where, and if so how do I check it. Any advice, suggestions, or help would be so greatly appreciated. Thanks in advance.

definitely sounds like a blockage of some kind given that you went through so many pumps. either that, or you are incredibly unlucky with the used pumps you buy.

have you cleaned or checked the injectors themselves? older cars like our 1985s (I have a 745t of the same year) have larger injectors that are less prone to blockage (newer ones are much finer and can be adversly affected by the smallest crudoo), but anything is possible.

have you tested the fuel pumps outside of the car in a water jug just to be sure they're shot? Resoldered or replaced the fprelay? I favor the latter since its an integral part and a new one can be had online for less than $30, but everyone has their own preference. btw, like a numberof the relays on this car the fpr always runs a little hot. fyi, I'm actually playing with the diea of mounting a temp. actuated fan on the back of the firewall in the relay compartment to blow air over the relay board... SOOO hot in tehre sometimes.

you state that the pre-pump works, but have you pulled the sender assembly/arm out of teh tank and checked it? maybe your pre-pump screen is clogged? maybe teh sender itself is corroded? this happens because the sender assmbly is exposed on teh back of the tank... my sender's power cable rotted off a few months back, and the sender itself was pretty nasty on teh outside.

also, look inside your pump or rip one of the busted ones open and see if you can find any goo or crudoo that may have caused it to burn out.

If none of the above works, you might want to pull all your fuel lines and check to make sure they are clear. However, I would view this as a last ditch since any of the crud blocking your lines should evident in the pumps or filters themselves.

hopefully someone who has experienced this problem will post.

good luck,
rt

Ypu have to check the in tank pre-pump as well as the connecting hose. The hose may be more holy than righteous. Access is in the left side of the trunk by the wheel arch. There is a plastic cap. Station wagons are similarly situated. Check the 700/900 FAQ via the 'features' pull down menu.
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Warren Bain - '86 744Ti M46 >285Kmi, '96 965 >99Kmi Wifemobile near Manassas Va.. I get e-mail replies to my postings.