Fuel pump power issue...

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Read again post #14, you quoted it and said i's good advice then neglected it... it's about voltage on the relay's coil not other coil... if the voltage is low that's why they are buzzing and not closing
 
Yup, hands up. I didn't deliberately miss that part of your reply, I want to solve this problem. Your advice has been appreciated. Thanks.
 
sierrafery said:
Read again post #14, you quoted it and said i's good advice then neglected it... it's about voltage on the relay's coil not other coil... if the voltage is low that's why they are buzzing and not closing
Click to expand...

Morning, so I've measured the voltage across the relay coil (ignition on) & it reads 10.4 volts. What does that say?
 
85-86 is OK, the voltage is low, at 10V is normal to not close well... now check across body and 85 then 86 and report both readings
 
So, I'm writing all this to make sure I'm measuring correctly:
The black plug relay ( the main relay ) with the ignition on & with an earth supply with a cable directly from the battery
86 (with thick brown wire) reads: 11.92
85 ( with blue/red wire ) reads: 1.87
 
You measured well, at this point i'd say to stop the struggle and try to find a known good ECU to rule yours out cos that 1.87V on the UR wire is no OK, the ECU should internally switch to earth on that wire with ignition on as to close the relays, now you have voltage both sides of the relay's coil that's why it's buzzing. Also i'm sure that the ECU doesn open the injectors either which would happen only if it's immobilised, it doesnt get battey feed or it's faulty. IMO the faulty ECU is the best scenario cos it can be a wiring issue too between the ECU and relays/injectors and that can be a nightmare to troubleshoot also feckless untill the ECU is not confirmed 100% in working order.
 
sierrafery said:
You measured well, at this point i'd say to stop the struggle and try to find a known good ECU to rule yours out cos that 1.87V on the UR wire is no OK, the ECU should internally switch to earth on that wire with ignition on as to close the relays, now you have voltage both sides of the relay's coil that's why it's buzzing. Also i'm sure that the ECU doesn open the injectors either which would happen only if it's immobilised, it doesnt get battey feed or it's faulty. IMO the faulty ECU is the best scenario cos it can be a wiring issue too between the ECU and relays/injectors and that can be a nightmare to troubleshoot also feckless untill the ECU is not confirmed 100% in working order.
Click to expand...

Oh, I'm fast getting out of my comfort zone, I was hoping I could fix it without needing to mess around with the ecu. Hey ho, I need to decide if I wish to continue, I need to find out how much a new ecu is, if it's expensive then I may need to re-think & let the car go. It's a shame because she is in really good shape for 27 yer old, low miles 104k & great history, only 2 previous owners, the last owned it for 23 years.
Hmmn, I wonder if anyone on this forum has an ecu I can try before buying one..I'll ask. Thanks for your help thus far.
 
In addition to the above, a last thing you can do is to check for voltage on ECU's plug across the black wires and pins 15(brown) and 19(white red) with ignition on to see if it gets feed. Maybe you are lucky to be a missing earth to the ECU.

I'll try to explain in a nutshell: The ECU must get feed on those two pins with ignition on then it should close the main relay which provides the feed to ''activate" it as to close the pump relay and manage the injectors. If this condition is not met the engine cranks but will not fire. Im not sure how the immobiliser acts on these engines but on some others an immobilised ECU would do that
 
sierrafery said:
In addition to the above, a last thing you can do is to check for voltage on ECU's plug across the black wires and pins 15(brown) and 19(white red) with ignition on to see if it gets feed. Maybe you are lucky to be a missing earth to the ECU.

I'll try to explain in a nutshell: The ECU must get feed on those two pins with ignition on then it should close the main relay which provides the feed to ''activate" it as to close the pump relay and manage the injectors. If this condition is not met the engine cranks but will not fire. Im not sure how the immobiliser acts on these engines but on some others an immobilised ECU would do that
Click to expand...

OK thanks,I will try that...
 
Might be that ... can you read the part number of the ECU? it should have a label on it
D1 V8 ECU earth.jpg
 
JDZ2 said:
I don't understand what you mean....left hand side head, please be more detailed...
Click to expand...
on the rear of the left hand side head, are the efi earths,efi loom is separate to car loom and is plugged into car loom above drivers footwell , the earths for the loom bolt to the cylinder lhs head
 
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