fuel relay

[dfw325e]

hey everyone..i have a problem i cant figure out. 1985 bmw 325-e...car wasnt starting and i took the fuel pump relay out and jumped the 87 to 30 wires...then i could hear the pump work...so i bought a new relay and still have the same problem..fuel pump will only work when 87 and 30 leads are connected. Ive tried a couple relay's so i know it cant be a bad relay..so what else could it be. The car runs perfect w/ the two leads connected. Please help

[jeffreyb4me]

I'll try. The car runs [fuel pump runs] jumping pins 30 & 87 in the plug because your by-passing the control portion of the relay.
A brief review: Bosch relay pin I.D.
30 = Battery [B+ or KL30]
87 = switched load circuit
86 = relay control coil supply, Ign. on voltage [KL15] - powered from the ign. switch in the on postion [#2] or other control relay.
85 = relay control coil energize circuit, controlled by another component IN THIS case the DME control unit.
This is done in the fuel pump's case as a required crash saftey feature, in a crash where the engine stalls but the key remains on, this will shut the pump off [ pumping fuel = fire hazard ].
Since you say it runs by jumping 30 & 87, the Main Relay is good as one of this relay's two #87 pins powers the DME Control unit, the other powers the fuel injectors AND pin 86 of the pump relay. You can confirm this by [with a fused jumper] grounding the fuel pump relay pin # 85 [Brown/Green wire] with the relay plugged into it's socket. IF the pump runs, the problem is between the relay and the DME CU or the DME CU itself.
BE SURE you have the correct relay and the pins and wires match.
BE SURE you have B+ at both pin 30 & 86 with the key on.
30 = red
86 = red/white
85 = brown/green
87 = green/violet
Best to you, hope this helps.

[futball22]

I had a simular problem with my honda after i swaped in a new engine, i found that just by running an aditional ground wire, it worked fine. I'm not too sure what changed the situation, but i had the same conditions. After hard wiring the 2 wires i had perfect fuel pressure, so after buying a new fuel relay, and putting it in it never changed everything. so i took a gatorclip, and connected it to the ground wire on the harness, then connected the other end to a good ground source. My car started right up. But after cutting the ground wire and re-grounding it where i did before, it wouldn't work again. So i had to reconnect the original ground, and splice in an aditional ground wire to it, and after that it ran fine, and still does.

[dfw325e]

hi, and thanx for your imput about the fuel relay problem. How exactly should i ground the #85 pin with the relay plugged in? Also i should add when i changed the relay with a new one the car ran for about 30 min. i took it for a drive and everything was fine until the end it started to studder and loose power shutting off at idle. i would restart it and it would drive a little and studder again. after i got it home it sat for about an hour then would not start again. While jumping the wires i can hear both fuel pumps running..anyway thanx for any advice..im at a complete lose and cannot afford to send it to a shop.
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Jefferyb4me wrote:

Fabricate a jumper lead from an in-line fuse holder [they come with a wire on esch end]. Extend the leads if needed with some 18g wire, crimp on a couple of aligator clips to the ends and install NO MORE than a 10 amp fuse of the appropriate type.
When testing with this type jumper ALWAYS clip the ground clip FIRST to any clean chassis or engine component.
In your case, clip the other aligator clip to the underside of pin #85 and start the engine. If it's runs completely normal after an extended period and through some retries, you've narrowed the cause.
NOTE, through this jumper WILL NOT protect sensitive IC circuits it's fine for your intended purposes here {after a load in the circuit (the relay's coil)} and if you error in your connections [jumping from B+ directly to ground, the fuse blows instantly protecting the circuit]
Hope this helps, ...................jeff b.

[dfw325e]

Okay, I grounded the #85 pin and the relay works. Seems like everything on that end is working...but a have a another problem! It will run fine like new, and all of a sudden i loose my tach reading from 3 to 0, the engine seems to be running but w/ no tach or gas power. I shut the engine off and turn it back on and she's running again? Any suggestions?

[jeffreyb4me]

This kind of confirms my suspicions about your DME Control Unit during my explaination of the pump relay's operation. While there can be other causes for a tach. malfunction [SI Board, main board, the tach itself], if I understand the last part of your statement, IF ALL ELSE FUNCTIONS NORMALLY, but without more info, I'm throwing darts.

[futball22]

The way i did it was to attach another ground to the existing ground wire. Dont ground any (+) wires, take the existing black wire, and from the back of the harness coming from your car to the relay, connect a gatorclip to there and attach it to a ground source. I dont know what it did exactly, but it solved all of my problems with my car. I figured maybe the ground just wasnt strong enough, so after i attached a aditional ground to it, it grounded itself better and worked fine.

[dfw325e]

hey everyone thanx for the feedback. Well let me try to explain this. When i turn the ignition on i hear both pumps running, but they never shut off. The car will start and run for a while and then it just dies. Like its the gas presure. I was thinking the main relay or another relay b/c seems like when i shut the car off and start it again i flipped the relay and it runs for a little while longer until it does it all over again. Could it also be the pump is running but running weak? I can hear it humming and it never seems to stop.

[dfw325e]

i should also mention only while im driving it..not really on idle.

[jeffreyb4me]

1] on E30's the pumps should run about 1.0 sec. then stop, when the keys's turned on but the engines hasn't been started...PROBLEM
2] be SURE you've got the correct relays [Main + Fuel Pump]
3] it's really time to invest in a fuel pressure gauge and SEE IF the problem is FUEL or something else.
4] yes, it could be the main pump BUT it could be many other things. Time to stop throwing darts and get more evidence.

Stay in touch............................jb.

[futball22]

you should be able to see how long the pump runs for by just turning your key to on, but not starting the car. You should hear the pump turn on, then stop, I dont know much about bmw's but according to jb, it should only run for 1 sec. and most other cars its around 3 seconds or so. A quick way to check for pressure would be to look for a bleader screw on your fuel rail, you could crack that open and get someone to turn the key to on, it wont have enough pressure to shoot gas everywhere, but you definatly will see it bubble out. The only problem with that is that you cant tell how much pressure you are getting, so it will show that your pump is working, but not how well.

[dfw325e]

okay well the main pump outside the tank is definitly running w/out turning off..and it is also is noisey. I dont have a pressure gauge yet but it does seem like i have to let the pressure in the lines build up so the car will start...but will this cause the car to die once its running? Also how do i know if its the transfer pump in the tank or the main pump?

Thanx for all the feedback!

[dfw325e]

also, it is imperative to have a fuel pressure gauge w/ a bleeder on it?

[bigman348]

I have a 1985 325 Manual transmission. It started as an extended crank problem. And then it turned into a no start. It would start some times after it sat for a while. And now it just won't start at all. Do you have any start points for me. I am a mechanic for a pontiac gmc hyundai dealer but don't have any information on bmw's. Thank you very much for any information.

Matt

[dfw325e]

okay i think i figured it out!! there was a ground wire that was loose and it seems when i tightened it the car will stay running. the only thing is i sprayed cleaner in my idle air stab. valve and the idle is very high. I have a tester but not sure how to go about using one. the manual says i should be between 400 & 500ma..how do i set my tester and touch the wires to the valve.

As for the no start prob matt listed i would check the fuel relay first