fuel pump issues

[mariner]

2001 Chim 500

After searching the forums and looking at the wiring diagrams I am at a loss.

Symtoms are:

1.Immobiliser seems to work and engine cranks over.
2. Main relay clicks and in turn supplies power to +ve side of fuel relay control
3. Fuel relay itself works when swapped with main one
4. Fuel pump works when hot-wired at relay block
5. Checked fuse in box and one or two either side, think I got the correct one since the alarm piped up when I pushed it back in, bible says there is an alarm feed on the same fuse. (this would be the supply for pump I guess)

So I can get 12v at the +ve terminal but the -ve terminal of the control circuit is not being earthed.
This is a blue/purple stripe wire. The two wiring diagrams I have say that it goes back to the ECU (possibly pin 16 Ignition coil -VE)?

Any ideas welcome, off to go look at the coil?

Thanks

[lwt]

If the relay is OK and the pump runs when hot wired, the problem may lie inbetween. Up under the glove pocket is a hinged access panel that conceals an inertia cutoff switch. This is just some contacts and if you decelerate too quickly a ball bearing rolls up a slope and knocks the contacts open. A dash indicator light (I think it's an exclamation mark '!') should come on at this point, but didn't on mine. You can push a button and re-make the contacts. On mine the contacts tarnished, so that volts got through but not much current. The test for this is to replace the fuel pump with a bulb (sidelight or similar). If it is only dim, poor contacts are your problem.

I can't recall the wire colours,but there is also a multipin connector block behind the door (pull back the triangle of carpet to show a fibreglass panel - I think its held in with velcro. Behind that is the door solenoid and the connector. You do the lamp test here too.

Stick at it, you'll figure it in the end!

Ian.

[spend]

The ecu probably switches the grounding of the fuel relay if the engine is not cranking, looking for a static -ve will possibly only show when you first switch the ign on, then flick off after a while

Dave

[mariner]

Thanks lwt

forgot to mention that I have checked the inirtia switch.

Since I have hot wired the pump at the relay connector block with a bit of wire with a spade either end, I would have thought that I can assume that the pump circuit is ok from here on. Whirrs up strongly like normal.

[mariner]

btw

re spend - ECU switches the -ve of the control circut

Does anyone know..
Normal startup pump whirrs for 5 sec and stops until engine is started(cranked) fuel pressure is lost in the rail.

There is a sensor which clicks every two - three secs screwed into the rail.

What stops the pump when fuel pressure is reached? and therefore turns off the fuel relay.

[mariner]

Engine will fire and run for a second or two as normal, with residual pressure in the rail from hot - wiring the fuel pump

On another thread a mention was made of another fuse, but on mine there are no more I can see, and the ones near the alarm in the dash are ok.

[spend]

mariner said:

btw
re spend - ECU switches the -ve of the control circut

Exactly... but it stops if the engine is not cranking (the dizzy feed to the ECU) after a while... Bit confused by your response, all I was saying was to make sure you were testing it at the right time, I'm not sure the ecu keeps it to ground all the time?

Dave

[mariner]

Thanks spend for your replies

You are saying that there is a feed from the dizzy to the ECU, to tell it that the engine is not turning over (cranking or running).

Normally, ignition on, fuel pump whirrs for a few seconds and then stops.

(If the ECU grounds the -ve control for a short time and then stops because of no cranking then this is not happening)

Something stops the pump, is it either
A) ECU realises due to no cranking/running or
B) A pressure switch in the fuel rail.

reading into what you are saying then the answer is A

I have had the digital multimeter hooked up the the terminals on the fuel relay block when disarming the immobiliser.

Main relay clicks and the voltmeter jumps slightly but only a fraction of a volt.

Certainly not 12v for a few seconds after switching on/de-immobilising


Sorry to press on but I don't have a spare ECU to try.

The feed from the dizzy, is this of a particular voltage. I could try to trick the ECU into thinking the engine was turning.

[spend]

Dizzy sends a pulse (ecu & rev counter just monitor the coil actually & ecu obviously bases a lot of decisions on how fast the engine is spinning..). Just switch ignition key off, then on, ecu will certainly ground the fuel relay for >10secs I would guess, I dont know the exact timings, but it would just be sensible to test under these conditions IMHO

Dave

[bsdnazz]

Both the starter solenoid and the fuel pump are wired through the immobiliser. My immobiliser had to be replaced after the starter solenoid relay started playing up.

It's possible that your immobliser fuel pump relay is playing up.

[GreenV8S]

Confirm that when the ignition is on you get +12v on one side of the relay control circuit. When you earth the other side of the relay control circuit (via a fused wire) the pump should run. If not, check whether the relay is actually operating when you earth it.

When you switch the ECU it should energize the fuel pump relay for about three seconds. This is just timed and not anything to do with fuel rail pressure. If it doesn't do this then you need to investigate why, but bear in mind that you only have three seconds to do your testing each time you switch the ECU on. If it *does* do it then find out whether it's also energizing the relay while the engine is cranking. If not, you are looking for a fault in the ignition circuit, or the wire from the dizzy to the ECU.

[mariner]

Thanks Spend

I have continuity from pin 16 on the ECU plug to the -ve on the fuel relay block. so at least I know it goes there.

I have had the voltmeter plugged in at startup and no joy. no voltage across fuel relay control terminals as soon as you disarm and turn it on. Nor when cranking. But have got +15v on the +ve control side.

So it would seem that the ECU is not grounding pin 16. Also I have checked the ECU terminals and plug which are all clean and tight.

Does anyone know if Carl Baker is back from his honeymoon yet? Thinking of phoning him tomorrow re the suggestions of the fuel pump being wired into the immobiliser as well as the starter.
Can't really see this though since the car will run if the fuel pump is hotwired across the relay terminals.

Please don't say my ECU is fubared.

Any further ideas? I'm at a bit of a loss as to what to try next.

Edited by mariner on Monday 7th January 22:14

Edited by mariner on Monday 7th January 22:18

[spend]

Nah, the immob is in the same bit of power circuit as the inertia switch. Someone might have put the coil signal thru the immob - but that is quite rare? Just hotwire the relay (2 // connected to the perpendicular one in a row down the middle) and you can check if it starts (pump will run while you have link in) -coil signal will be ok if it fires up

Dave

[mariner]

yep pump runs if I hotwire the connections on the relay block.
And the engine will fire up.

Just not getting a ground through pin 16 on the ECU. (-ve side of fuel relay control)

Edited by mariner on Monday 7th January 23:36

[spend]

mariner said:

And the engine will fire up.

And it stays running OK??? not just fire up & then cut out?

Dave

[GreenV8S]

mariner said:

yep pump runs if I hotwire the connections on the relay block.
And the engine will fire up.

Just not getting a ground through pin 16 on the ECU. (-ve side of fuel relay control)

I would be looking back along this circuit for a poor connector or dry joint inside the ECU, then.

[mariner]

Found it, Yay!

Opened up the ECU and found the eeprom converter socket was 2mm high on on side pushed it in, closed up and tried it and bingo!

Thanks to all who have replied

Richie

[spend]

I wonder if they run better with the eprom pulled out then?

Dave