fuel pump wiring

mrobin · 12-22-2005, 02:51 AM

hi.
when i turn the ignition switch the fuel pump doesn't work. when i wire the pump direct from the fuse box, it work fine and the engine runs. question, outside of the possible dangerous results it i get in a crash (fuel pump won't turn off) is there any thing wrong with wiring the pump this way ????
This is just a temporary wiring until I figure out what is wrong the the ignition wiring to the pump.
thanks
mike

Kevin Powers · 12-22-2005, 07:44 AM

fi or carbs? more info shortens the path to success.

k

swl · 12-22-2005, 03:54 PM

what engine? Ljet is different than Djet.

There was another thread, either here or at the 914 club that talked about picking up the power from the coil. Seems to be a common work around. Yes, there is a safety issue. Better to track it down. A few minutes with multimeter can find most problems. I'd be happy to talk you through it.

mrobin · 12-23-2005, 01:23 AM

hi
it's a 72 1.7 with FI (d-jet) and the fuel pump has be moved to the front of the car. I'm a real mooron with electrics so any help will have to be in language for idiots to understand.
thanks
mike

Clay Perrine · 12-23-2005, 05:53 AM

In the ringht front corner of the engine compartment, below the hell hole, there should be 2 wires, one black with a red tracer, and a brown wire. The black with a red tracer should be extended to connect to the positive side of the fuel pump. You can hook the ground wire up to any ground point.

On a D-Jet car, the fuel pump is controled by a relay, and that relay is energized by the FI control unit (I can't call something that primitive a computer). With the wiring hooked up as diagrammed above, jumper the relay and see if the pump runs. to jumper the relay. On the relay board there are 4 relays. The one you want is the second from the rear. locate pins 30 and 87. Connect them together. If the pump runs, try replacing the relay. Don't replace it with the second from the front, that powers the FI control unit.

Try this stuff and let me know the results.

swl · 12-23-2005, 06:33 AM

Here is a diagram for reference. I don't know where I scooped this one from but I really want to thank the guy who did it - it is great. If anyone knows who the author is please let me know. I'd like to suggest some additions to it.

It may loose some resolution with the boards automatic resizing. If you cant read it pm me with an email address and I'll send it to you.

In addition to the fuel pump relay that Clay mentioned there are two other components to check. The power supply relay - it feeds 12 volts to the coil of the fuel pump relay when the iginition is on or start. And the 25 Amp fuse - it supplies 12volts to the fuel pump through the fuel pump relay contacts.

If your headlight motors are working properly their relays are a good low tech way of testing the relays - they are the same ones and give you instant feedback as to whether or not the relay works. BTW be careful how you pull the relay. The tops can pop off them leaving you with a plastic cup in your hands rather than the relay.

Fuse should have 12 volts on both sides. If you don't get 12 volts on the drivers side then replace the fuse. Cleaning up the contacts is also a good idea. If you don't have anything to check voltage with your heater fan is fed by the same fuse. If it is working then the fuse is probably good.

Check those 3 and let us know.

Clay Perrine · 12-23-2005, 06:48 AM

The power supply relay and fuse won't be the problem. The power supply relay and fuse supply power to run the FI control module. If it was bad, the car won't run at all.

that is a nice diagram of the relay board.... Where did you get it?

swl · 12-23-2005, 10:41 AM

Can't remember where I got it but it has been a life saverr. Thought it was here but can't find it again. Might have been on a thread at the 914club.

You are right about the main power relay - missed that part where he said it runs fine in the by pass mode

I think it could still be the fuse. It seems to power only the fuel pump, heater fan and rear defogger - red line from the left side of the fuse. The ECU gets it's power from the output of the main power relay - black line.

Dave at Pelican Parts · Dave at Pelican Parts's Garage

If you bypass the fuel pump relay, the pump will run even with the ignition off. BTDT when trying to manually do a "limp home mode" band-aid one day. I had to remember to pull the jumper or the pump would run until the battery died.

There are two excellent D-jet fuel pump diagnostic articles out there. One is all text-- http://www.914fan.net/fuelpump.html The other uses flowcharts-- http://members.rennlist.com/pbanders/FPChecklist.htm .

I posted those links on the "other board" (and also, I think, through our on-line Tech Support mechanism, if this is the same guy) but I figure it would be good to have those links here just in case someone goes searching for solutions.

--DD

Clay Perrine · 12-23-2005, 12:59 PM

Dave,
You can jumper 30 to 87 on the fuel pump relay and the pump will run with the key off. If you jumper 85 to 87 the pump will turn off with the key. But that is powering the pump off the FI power circuit and not the fuel pump circuit.

Dave at Pelican Parts · Dave at Pelican Parts's Garage

Yikes! I wouldn't run the pump off of anything but its own circuit! (See my earlier comments on running it off the coil, too.)

--DD

Clay Perrine · 12-23-2005, 08:07 PM

Neither would I, but it CAN be done.

mrobin · 12-24-2005, 01:16 AM

clay
thanks for the imput. I will try them out this weekend and let you know what happens.
thanks for all your help.
mike

mrobin · 01-06-2006, 02:04 AM

update...
told you i was stupid... it was in fact, the relay, put a new one in and everything is ok.

thanks for all your help....