Hi All,

I am currently putting a 1990 XR3i EFI back to 100% standard. I have just finished rebuilding the head (everything new) and cleaning up.
https://passionford.com/forum/album....ictureid=25249
One major prob. She's all show and no go!

On turning key no fuel pump prime. I have checked relays (both one yellow in yellow holder and one yellow with fuse joined at side in black holder) both work fine.
https://passionford.com/forum/album....ictureid=25250
https://passionford.com/forum/album....ictureid=25251
Focusing on the yellow relay, in yellow holder. I bridge contacts 30 and 87 and the fuel pump primes. However the relay is good. On checking the plug all contact are live except 87 even with ignition on or off. Any ideas if this is right, as what would trip relay?

I have checked switch in boot and thats fine too. Is there another relay I'm missing or is one of these not the right one? any ideas please guys!!

 

Have had a thought about this and could it be the ecu is not sending a negative pulse to fuel rely to switch it? If so possibility of faulty ecu, our sensor such as cps? Any ideas....please

 

The relay is generally triggered via the ECU, in most cases it requires the CPS signal to do so, if you have check for spark then the CPS is working.

I should think, there is only one relay for the pump?

Martin

 

Thanks Martin. I wil crank it over with a plug out and look for spark. I gather that if I have a spark the the CPS is fine?? Will have a go. I hope it is just the crank position sensor otherwise I'm getting stumped. Cheers murph

 

Check around battery for a thin brown wire which needs to be connected to the battery earth, I missed this when rebuilding my efi and had exact same problem. Thought I'd messed something up!

It had fallen away from the other earths and was sitting against bulkhead. I believe it's the earth for the pump relay and the power comes from the ecu.

 

Cheers will defo check all battery wires now that are not main ones. Makes complete sense as I'm getting a live on the earth. Hoper its this simple! Cheers

 

Just an update. AstoN_B you were spot on! The earth connection from ECU to batt was faulty. Small break in cable. Repaired and pump primed. Took a bit to get her going and was a little rough. Few trips round the block and the ECU settled down nicely and learn't the pattern. Now purring like a kitten. Well chuffed!
Head rebuilt and now for the body work inspection and respray, then retrim etc etc.....

 

It didnt even occur to me that it could be the ECU earth, i assumed fuel pump relay cause i'd been messing installing a hidden cut off switch to pump. But in my case it was obvious once i saw an earth sitting there when it should have been bolted to battery with the others.

Glad you're sorted!

 

Hi people I no this post was from years ago but I'm having the same sort of issue
Just read about a brown wire to the battery earth from the ECU I cant seem to find any earth wire