Fuel Pump Electrics

[Guest johnboymac]

Ive connected the electric fuel pump for my injection system, but when i connect the battery (with the key out of the ignition) the fuel pump kicks in and continues to run, it does not cut out even when the system is full - I can hear the fuel pumping directly back into the tank. Im happy to see that the fuel system works, but there must be a problem for the pump to come on with the ignition off, and for it to continue running as it does - any ideas - could it be the relay?

 

cheers guys.

john

[Guest Guy]

Hi John,

 

If you unplug your fuel pump you should be able to hear the relay in the fuse box click in when you turn the ignition on and then click out again after about 1 second.

 

If it doesn't do this then somthings wrong. If the contacts are stuck together then it'll give the fault you describe but it's unlikly to happen.

 

Have you taken the + feed for your pump from the correct place?

 

Mines probably slightly different as I cut most of the wires out of my loom and fusebox and started again.

 

I've got the original Sierra diagrams at home so I'll have a look tonight.

 

Just as a note of safty, you can replace the fuel pump with a 12V bulb for testing, it wont pump any fuel but you can see when it's on.

[Guest Ant]

Is the ECU connected up correctly, and fully earthed etc?

 

When you switch the ignition to II the fuel pump should come on for about 2 or 3 seconds, and then go off. It next comes on when the ECU see's that the engine is turning - ie it waits for the signal from the dizzy, and so long as the dizzy is turning it keeps the fuel pump on.

 

Sounds to me like the fuel pump relay is fine, otherwise it wouldn't come on at all. The ECU should be wired in to drive the relay, and it sounds like this is permanently in the "on" state.

 

Ant

[Guest johnboymac]

Ive got home and checked things this evening. Fuse 23 is 20a

relay d is a blue one and is not the same as the one in the haynes manual, but swapping it with a brown relay (with the same markings as the manual) sees no power getting to the pump.

 

with the blue relay in pos d, the feed to the pump is live, with the relay removed or swapped out for a brown one, no power.

 

Im not sure how \ what to check at the ecu, but I didn't do anything with this other than put the big multiplug in and tighten the screw.

 

any suggestions ant\ guy, the local scrappy is a part-time highway robber \ mexican bandit so I don't want to get another ecu if I can avoid it (he asked me for £25 for a very rusty fuel pump at the weekend with no guarantee that it would work - i declined as I was only looking for a spare anyway.) But Im a little worried that it may be the ecu (which would cost) related since the wiring from the fusebox is getting power.

Im not sure about other relays though - I have nothing in engine management relay XI and I also don't have an inertia cut out switch as far as I can see? though this appears to be in the manual.

[Guest Ant]

I'd be surprised if it's the ECU - more likely to be one of the wires not connected or a missing earth or something like that.

 

First thing would be to trace through the circuit diagrams and work out which two connections on the relay are joined to power the pump, and which two are the power for the relay. Then try joining the pump ones with a wire - the pump should come on. After that trace the two wires which power the relay. Do you get 12v at any time when you switch the ignition from 1 to 2? It should be powered for about 2 or 3 secs and then be nothing again.

 

On the ECU connection, remove the plug and use a multimeter to check that every connection joins to other parts of the loom in accordance with the haynes wiring diagram. This means disconnecting the battery and testing for a circuit between a pin in the ECU and pins in other connectors around the engine bay. Check the earths too. It's a 3 man job really and takes about an hour. One with the haynes book, one with a probe at the ECU plug, and probably you to unplug other stuff as needed with the other probe. Tick them off as you go. Check especially the wires to the ECU from the fuse box, and the ones to earth.

 

I went down this route twice before my engine ran. First time it was a missing earth ... second time it was a broken dizzy, but I had the 2 seconds of fuel pump running which is what you don't have, so I don't think it's the same fault.

 

Ant

[Guest Guy]

The blue relay is normaly closed, that is why the pump runs when it's in place. The brown relay is normaly open, that's why the pump doesnt run when it's in.

 

It sounds like the power for the pump is correct but the controll for the relay is not working.

 

You need another relay in to make the fule pump relay work but I can't remember off hand which one it is. I know that if you remove it or you have the wrong colour one in it's place then the fuel pump relay doesn't engauge. I suspect that if you had one relay wrong then you could have this other one wrong as well.

 

Have a look at THIS PICTURE and check that you have all the relays in the correct place.

 

If they are all correct then you'll have to do the fault finding as Ant sugested.

[Guest johnboymac]

guy,

 

I have a couple of different coloured relays (or missing ones) than what you have in the picture. My fusebox\loom came from a cvh carb'd engine. The loom does match otherwise, but the relays appear to have been left off if not reqd.

I will be able to take a scrapyard trip on saturday. There was a sierra with a v6 pinto there last week(hmm wonder if that would fit a sub-k?) which had an injection setup ( I obtained banjos and electrical connectors etc), I checked its fusebox and if IIRC it looked pretty much a match for yours, so hopefully I can swipe what I need from there.

 

In the meantime, I guess I can do something else on the car.

 

thanks, John

[Longboarder]

John, I know this may sound as if I'm being real slow but I'm not clear of your setup. Are you trying to fit together a 2L injection pinto, electric pump, cvh (carb) loom and fuse box. What engine management ESC/EEC unit are you trying to hook up to this and what engine loom.

 

Nigel

[Guest johnboymac]

hi, nigel

 

When I realised that the cvh engine was a no go, I obtained a pinto engine complete with engine loom, and all ancillaries inc eec etc. The fusebox and loom from the cvh, is basically the lights, heater and fusebox itself (along with pump feed wire). On looking at the haynes, the wires are all consistent, the problem does seem to be centred on the relays (or lack thereof!) when I replace the blue relay for a brown one (the horn relay as it turns out) the pump has no power, but as guy is saying above, this is because the brown relay is open by default, it needs another relay to kick it closed - From looking at guys picture, I can see that I do have at least one missing relay - one of the missing relays is marked in the haynes as engine management relay XI.

 

cheers, John

[Guest Guy]

That's the one you'll need. I only have 3 relays pluged into my fuse box.

 

1 - A big one that runs all the electrics when the ignition is switched on

 

2 - the engine management relay XI (the one you've not got)

 

3 - the fule pump relay

 

all the other relays in my car are loose as I've done all the other electrics myself.

[Guest DaveB]

Correct me if I am wrong but the Haynes manual refers to the engine management relay 55 this is where the supply for the pump is derived from. On my donor loom this relay is not in the main fuse/relay board but in the engine management loom Yellow in coulour.

 

Dave B