agen7seven

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.

RyanPerrella

it should prime for a few seconds with the key in position 1 or 2 before trying to start.

iirc it only does this for less then 5 seconds

Mrmerlin

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.

RyanPerrella

you sure?

i diagnosed a faulty pump on my 90 because the pump was silent when the ignition was on.

Glenn Evans

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.

Glenn Evans

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.

John Speake

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.

agen7seven

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.

John Speake

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...

Rod Underwood

The pump should NOT run without the engine cranking, I almost found this out the hard way. I had an engine full of gas because the LH was bad and would allow the pump to run without the engine turning. Luckily we never hit the key to turn it over. We discovered this when DR was installing the twin screw and we could smell gas when he was programming the new chip. He had to power the LH to program it and when he did, with no program, the injectors were open and a stream of gas running out of the back of the supercharger with no engine crank... Dave then verified the problem and I had it rebuilt.

Rod

agen7seven

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:

the flyin' scotsman

That mystery box looks as if it was made in a 101 electronics engineering lab.

No idea of function but if disconnected does the car start?

Tampa 928s

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.

Tampa 928s

Looking at your pictures again it has mirror circuits, I would look to the twin distributors or injectors I think each bank is driven separately, just a guess.

agen7seven

Ok so I have now removed the box and reinstated the wires - still no joy.