XJ6 Series III Wont stay running longer than 5 seconds
#1
XJ6 Series III Wont stay running longer than 5 seconds
Any help is appreciated.
My car will start but won't stay running longer than 5 seconds. If I unplug the Air Flow Meter the car with run at 3k RPM but is undrivable.
Recent upgrades.
New alternator
Replaced Air Flow Meter with good used unit (I did this after the problem 1st happened it did not fix the problem)
Fuel supply is excellent both when starting and when manually activating the AFM.
New Pertronix distributor and coil.
I know timing is correct and that the replacement AFM is good. I also checked the fuel pump wiring and relay, both are good.
Could the AFM red diode be bad? Is it possible to bypass for testing?
Thanks,
Adam
My car will start but won't stay running longer than 5 seconds. If I unplug the Air Flow Meter the car with run at 3k RPM but is undrivable.
Recent upgrades.
New alternator
Replaced Air Flow Meter with good used unit (I did this after the problem 1st happened it did not fix the problem)
Fuel supply is excellent both when starting and when manually activating the AFM.
New Pertronix distributor and coil.
I know timing is correct and that the replacement AFM is good. I also checked the fuel pump wiring and relay, both are good.
Could the AFM red diode be bad? Is it possible to bypass for testing?
Thanks,
Adam
#2
Red diode? I presume you mean the red diode pack on the firewall? It works on the fuel pump control circuit. If your fuel pressure is good while cranking and running then I don't think you have a problem with the diode pack.
But.....
Running for just a few seconds does sound like a fuel supply problem. I'd bypass the control circuit and see what happens:
Remove the fuel pump relay. In the relay socket/plug locate the terminals that go to the white/green wires. Use a jumper wire to apply 12v to the white/green wire(s)*. You should hear the fuel pump run, Now start the engine end see if anything changes.
Cheers
DD
You might have more than one white/green wire at the socket (long story). No worries. Just apply 12v to each until you hear the fuel pump run. You can't hurt anything
But.....
Running for just a few seconds does sound like a fuel supply problem. I'd bypass the control circuit and see what happens:
Remove the fuel pump relay. In the relay socket/plug locate the terminals that go to the white/green wires. Use a jumper wire to apply 12v to the white/green wire(s)*. You should hear the fuel pump run, Now start the engine end see if anything changes.
Cheers
DD
You might have more than one white/green wire at the socket (long story). No worries. Just apply 12v to each until you hear the fuel pump run. You can't hurt anything
The following users liked this post:
Eurowerks (01-01-2015)
#4
Move to ignition.
Perhaps, the coil and distributor get voltage in the crank position of the ignition switch, but not on the run position.
A favorite basic diagnostic procedure of mine is to jump battery 12v to the + on the coil. Try again. If it runs, trace the wires back to the ignition switch. if sound, the "open" may be in the switch itself.
AKA known as "hot wiring" !!!
Carl
Perhaps, the coil and distributor get voltage in the crank position of the ignition switch, but not on the run position.
A favorite basic diagnostic procedure of mine is to jump battery 12v to the + on the coil. Try again. If it runs, trace the wires back to the ignition switch. if sound, the "open" may be in the switch itself.
AKA known as "hot wiring" !!!
Carl
#7
Trending Topics
#8
So I'm able to keep the car running if I push on the flap inside the AFM. I have removed the AFM plastic cover and the track looks to be in good condition. Any tips on what I should look for inside the AFM? Thanks Adam
It should be noted that I'm doing this while jumping where the two white wires enter the bottom of the red diode to engage the starter.
It should be noted that I'm doing this while jumping where the two white wires enter the bottom of the red diode to engage the starter.
Last edited by Eurowerks; 12-27-2014 at 03:12 PM.
#9
#10
Today I cleaned all grounds in the engine bay. I also inspected all wiring and made sure I was getting good fuel pressure from the starter and the AFM. I checked each of the injectors with a 12v source and inspected all engine bay wiring.
Still the same problem when I go to start the car. It starts then dies. It will stay running with the AFM unplugged but as you can imagine it idles high. As soon as I plug the replacement AFM back in the car dies.
I have even removed the top of the AFM to look at the stip and contacts. It's in GREAT condition. Very little wear.
Could this be the L Jetronic ECU/5CU? Is there anyway to test this?
Still the same problem when I go to start the car. It starts then dies. It will stay running with the AFM unplugged but as you can imagine it idles high. As soon as I plug the replacement AFM back in the car dies.
I have even removed the top of the AFM to look at the stip and contacts. It's in GREAT condition. Very little wear.
Could this be the L Jetronic ECU/5CU? Is there anyway to test this?
#11
#13
So I just had the car running without the AFM plugged in then I revved up the car and plugged in the AFM while wiggling the wiring harness at the back of the engine. The car started to sound better then a HUGE screeching sound came out of the back of the engine. I immediately killed power and the engine stopped running but kept Turing over as the starter had engaged. WTF.... Even with removing the key the starter wouldn't stop so I disconnected the battery -
This isn't very encouraging.
This isn't very encouraging.
#14
I suspect a wiring fault of some sort. The starter relay is probably being energized by a fault in the fuel pump circuit....most likely related to the red diode pack as that's where the two circuits cross. I think "+" voltage from the pump circuit is getting to the white/yellow wires
Do you have the S57 wiring book?
Cheers
DD
Do you have the S57 wiring book?
Cheers
DD
The following users liked this post:
Eurowerks (01-01-2015)
#16
Inside the AFM top box where the track is located is a pair of contacts that maintains engine running after you back off the ignition key when the car starts. They supply volts to the fuel pump relay and close when the flap moves open on engine start. These are notorious for not maintaining good contact after a few years, thus causing the engine to shut down due to lack of fuel. So check these out and clean them and also make sure they are making a good contact.
However, reading the thread, if you powered up the fuel pump directly, not via the fuel pump relay and the car still wouldn't run, then maybe these contacts are OK.
On my car I had the engine shut down whilst overtaking up a hill in traffic ! When I got to the side of the road and restarted it all appeared normal......until the next time ! Tweaking those contacts cured my problem, anyway.
Other thing is - are those injectors all ticking away nicely ? In my toolbox I have a special little light that plugs into a fuel injector plug, and enables one to check the pulse to the injector is there. The injectors rely on a good earth to work properly, but its too long ago for me to remember the location. On start-up, the cold start injector floods the engine with a load of fuel, so it will run for a few seconds on that.
However, reading the thread, if you powered up the fuel pump directly, not via the fuel pump relay and the car still wouldn't run, then maybe these contacts are OK.
On my car I had the engine shut down whilst overtaking up a hill in traffic ! When I got to the side of the road and restarted it all appeared normal......until the next time ! Tweaking those contacts cured my problem, anyway.
Other thing is - are those injectors all ticking away nicely ? In my toolbox I have a special little light that plugs into a fuel injector plug, and enables one to check the pulse to the injector is there. The injectors rely on a good earth to work properly, but its too long ago for me to remember the location. On start-up, the cold start injector floods the engine with a load of fuel, so it will run for a few seconds on that.
Last edited by Fraser Mitchell; 12-29-2014 at 04:54 PM.
#18
I found this fantastic write up on adjusting the AFM and wanted to share with the community.
Itinerant Air-Cooled Forum ? View topic - AFM Adjustment
Itinerant Air-Cooled Forum ? View topic - AFM Adjustment
#19
The car still won't stay running.
Timing is correct, the Pertronix distributor and coil are new. I've verified great fuel pressure before and on the fuel rail. Replaced the AFM and Red Diode. I ran a hot wire from the battery to the + on the coil to rule out the ignition switch. I cleaned all grounds and wiring connections, then treated them all with contact OEL. I removed all hoses and ensured they are tight and aren't leaking. The car will only run with the AFM disconnected or when I manually manipulate it while plugged in.
Timing is correct, the Pertronix distributor and coil are new. I've verified great fuel pressure before and on the fuel rail. Replaced the AFM and Red Diode. I ran a hot wire from the battery to the + on the coil to rule out the ignition switch. I cleaned all grounds and wiring connections, then treated them all with contact OEL. I removed all hoses and ensured they are tight and aren't leaking. The car will only run with the AFM disconnected or when I manually manipulate it while plugged in.
#20