Does the fuel pump prime - key on?
#1
Track Day
Thread Starter
Does the fuel pump prime - key on?
Ok, Yet another no start thread, but I have read conflicting posts on this. I believe the fuel pump should prime when the key is on.
Fuel pump runs when jumpered.
New LH computer (jds rebuild)
New distributor caps/rotors/belt/plugs - timing is right
All new relays
Injectors are showing voltage when turning car over
I suspect it has something to do with the ignition barrel.
Car is an 85 Euro S (twin dizzy)
Should the pump buzz with key on? it's not and I'm sure it used to.
Fuel pump runs when jumpered.
New LH computer (jds rebuild)
New distributor caps/rotors/belt/plugs - timing is right
All new relays
Injectors are showing voltage when turning car over
I suspect it has something to do with the ignition barrel.
Car is an 85 Euro S (twin dizzy)
Should the pump buzz with key on? it's not and I'm sure it used to.
#3
Team Owner
fuel pump does not start unless there is a pulse from the crank position sensor. So the engine must be turning
Are you sure that you have the distributor coil wires on the correct distributor?? If they are swapped the car wont run.
So can you please give as much info as possible is the car an auto?
What is the car not doing ? just saying it wont run is too brief of a description.
Are you sure that you have the distributor coil wires on the correct distributor?? If they are swapped the car wont run.
So can you please give as much info as possible is the car an auto?
What is the car not doing ? just saying it wont run is too brief of a description.
#5
Instructor
To add to what Mrmerlin has said: the pump wil run for about two seconds after an attempted start. The quick check of whether the fuel pump is operating is to listen at the back of the car while someone briefly turns the key to the start postion (for not long enough for the engine to start). You should be able to hear the pump run for a couple of seconds after the key is released.
#6
Instructor
If my last post is ambiguous, I am saying that Mrmerlin is correct that the pump will not run if the key is merely switched to the ON position.
If you are in doubt about whether the pump itself works, jump terminals 30 and 87 for the fuel pump relay in the relay board. If the pump doesn't run, either it is faulty or there is a fault in the wires to the pump.
If you are in doubt about whether the pump itself works, jump terminals 30 and 87 for the fuel pump relay in the relay board. If the pump doesn't run, either it is faulty or there is a fault in the wires to the pump.
#7
Rennlist Member
Do you have spark ?
Does the rev counter flicker when you crank ?
Fuel pump will NOT run until engine cranks (safety measure).
There will be volts on one side of the injectors as soon as igntion is on, the LH grounds the other side of them to pulse them.
Check that there isn't a short between injector wires in each injector, under their rubber boots. If there is a short it can damage the LH ECU.
Each injector has about 19 ohms resistance. They are wired in parallel, so combined resistance is only 2 ohms or so. Difficult to tell whether there is a short or not with some multimeters.
So disconnect all injectors, check that you get a high resistance when measuring between the pins of one of the disconnected harness plugs. Unplug the 25way connector to the LH ECU when you do this test.
Does the rev counter flicker when you crank ?
Fuel pump will NOT run until engine cranks (safety measure).
There will be volts on one side of the injectors as soon as igntion is on, the LH grounds the other side of them to pulse them.
Check that there isn't a short between injector wires in each injector, under their rubber boots. If there is a short it can damage the LH ECU.
Each injector has about 19 ohms resistance. They are wired in parallel, so combined resistance is only 2 ohms or so. Difficult to tell whether there is a short or not with some multimeters.
So disconnect all injectors, check that you get a high resistance when measuring between the pins of one of the disconnected harness plugs. Unplug the 25way connector to the LH ECU when you do this test.
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#8
Track Day
Thread Starter
Yes I have spark
Yes the rev counter flicks on start
To previous questions - it's an 85 Euro S, Auto.
I think the fuel pump is fine, I have tested it by jumpering at relay slot
I have checked injector plugs visually, will stick a multimeter on them tomorrow.
The pump is NOT running after an attempted start. Maybe the crank position sensor isn't working? since the pump runs when jumpered, but not when car is cranked by the starter. I will check and post back.
Thanks for your help guys.
Yes the rev counter flicks on start
To previous questions - it's an 85 Euro S, Auto.
I think the fuel pump is fine, I have tested it by jumpering at relay slot
I have checked injector plugs visually, will stick a multimeter on them tomorrow.
The pump is NOT running after an attempted start. Maybe the crank position sensor isn't working? since the pump runs when jumpered, but not when car is cranked by the starter. I will check and post back.
Thanks for your help guys.
#9
Rennlist Member
Hi Nick,
If you have spark, then the crank sensor is OK. If tach moves, then an RPM signal is getting to the LH ECU, and it should then wake up the fuel pump relay and trigger the injectors. when cranking.
So there is a contradiction there with what you are finding.
I asume you have checked all relevant relays.....
Also try unplugging the kickdown relay...
If you have spark, then the crank sensor is OK. If tach moves, then an RPM signal is getting to the LH ECU, and it should then wake up the fuel pump relay and trigger the injectors. when cranking.
So there is a contradiction there with what you are finding.
I asume you have checked all relevant relays.....
Also try unplugging the kickdown relay...
#10
Rennlist Member
Rod
#11
Track Day
Thread Starter
Just tried with kickdown relay removed, still no start. I got someone to listen down at the pump with cover removed. It is running on crank over, but it's not running anywhere nearly as loud as when the relay is jumpered.
There's also a mystery box spliced into the LH cable. I haven't mentioned it as the car had no problems before, but maybe this box is causing some sort of failure. Check the photos out:
There's also a mystery box spliced into the LH cable. I haven't mentioned it as the car had no problems before, but maybe this box is causing some sort of failure. Check the photos out:
#13
Race Car
Your box has a couple of driving transistors, large resistors and a couple of switching transistors so it must be driving a high current device. Looks Like they cut into the harness, have you verified the color of the wire in the harness and traced it? This must be turning something on its a good idea to find out what it does, find the circuit they cut into and you will have your answer.