prijedor

I have replaced mine back in 1999 on my 1989 200q and got about 70.000 miles since then.
I would be driving down the road and car would start stalling like it's not geting enough gas and fuel pump would get realy loud.I would pull over shut engine down and start it again,car drives fine like nothing happend.This has happend 3 times in last 3 months.About 3 weeks ago my ISV started to make engine run on to high RPMs when idling.Car was sitting for about 2 weeks till i got new ISV.Now with new part installed on most days fuel pump would start to make not constant buzzing sound,like it's skipping,and gauge would be moving back and forth in same rytham as fuel pump between 13-14 V.RPMs would be about 800-850.This is all happening while idling and at the same interior lights along with headlights would be flickering.Adjusting screw on throttle body is turned few turns,same as it was with old ISV.
Car has stalled once with new ISV.
Once i start driving car runs great,lights are not flickering and gauge is steady at around 13V.Fuel pump relay is about 3 years old and i don't see ani corosion on contacts or any signs on burning underneath cover of relay.
I have tried to install other 2 used relays and no difference.
Today i installed new Bosch fuel filter but problem is still there.
Can anyone say for sure what the problem is ?
I would like to replace right part before winter.I don't know how much longer my fuel pump will last.
I think someone said in old post that fuel pump going bad can damage fuel pump relay.
Any help is greatly apreciated.

prijedor

i will check back in morning.

Kneale Brownson

Have you tried something like Heet in you fuel tank?

prijedor

that is great next step in trying to solve this problem,thank you Kneale.

5000Q86

if all the lights are constantly going dim, bright, dim bright, and the fuel pump pitch is going low, high, low, high, then id suspect that the voltage regulator on your alternator is to blame, i had a similiar issue with my 100, minus the high idle and tendancy to die. the regulator smoothes out the voltage generated by the alternator to a contstant 14 or so volts. if that goes bad, all the lights, and anything drawing electrical current, including guages and (sometimes) speakers, will vary in pitch or brightness. you should have your alternator tested for free at advance auto parts, if your in the norwood MA, area, i can do it, i work at the advance on dean st.

audi_marv

Re:a bad voltage regulator/bad alternator will eventually fry your fuel pump too...

prijedor

and lights are only flickering when idling,during driving everything is fine.
I will go to Advance Auto Parts to get Heet and test alternator,that is were i got mine,it has lifetime warranty.

prijedor

Advance Auto Parts tested alternator and test has shown,like my gauge,that voltage when idling is 14.1-14.9.
They said that only by removing alternator and bench testing they can be sure that alternator is bad and nothing else.
I did get new regulator in case i need to replace it over weekend.
What would you guys do?

audi_marv

I would check the alt. connections and grounds. A bad ground connection could cause the light flickering. Check battery ground. Ground at fuel pump also for pump and gauge issues. Idle issue could be your throttle/idle sensor at front of throttle body. Plugs and air filter ok ? Have you checked for any codes ?

5000Q86

i had the same symptom with my 100, during idle, EVERYTHING would either change pitch or brightness, but appeared steady at higher rpm. if you wanna know more about how the voltage regulator does its thing, lemme know.

best of luck to ya

eric