Won't start, was fine last night

[nicktheviking]

Drove the spider fine last night. This morning, just cranks and cranks, doesn't catch.

I pushed the AFM flap, heard the relay click but didn't hear the fuel pump. Checked the inline fuse--it's fine. Do I have a bad fuel pump?

I'm going back out to check for spark so I can rule that out.

[nicktheviking]

Ok, what the heck. I was pushing on the AFM, trying to listen for the fuel pump and after several attempts, it came on. Cranked the motor and it started right up!

Any ideas on this? I'd hate to get stranded.

[nicktheviking]

OK, I'm pretty sure its the fuel pump. Now when I push on the AFM door, the fuel pump doesn't come on.

[rlux4]

You need to pull the 12V line at the fuel pump and see if it gets a signal when you open the AFM flap. If it gets 12V, then the pump is going out. If it doesn't get 12V, then it'a control problem. Something is not sending the voltage to the pump. I've had an inline fuse that would look good but not pass voltage because the holder wasn't making contact on both ends, you could check that also.
Let me know if you find the problem with these suggestions.
Ron

[nicktheviking]

You need to pull the 12V line at the fuel pump and see if it gets a signal when you open the AFM flap. If it gets 12V, then the pump is going out. If it doesn't get 12V, then it'a control problem. Something is not sending the voltage to the pump. I've had an inline fuse that would look good but not pass voltage because the holder wasn't making contact on both ends, you could check that also.
Let me know if you find the problem with these suggestions.
Ron

Thanks Ron. I'm pretty sure it is, as I've got the fuel pump to come on twice today. However, I'll climb down there with a test light.

[nicktheviking]

Update:

Still not working.

Ron advised me to check the brown/white fuse. It was tucked up behind the dash, so I missed it. Took it out, took it apart and it fell apart.

I stuck my test light in both spades (couldn't tell which came from the relay) and cranked it, but no light.

When I stick my finger in the AFM, I can hear the relay work, but I realize this doesn't necessarily mean it's working.

I think the next step is to inspect the relay, and maybe replace?

[rlux4]

Nick, to make sure we have all the bases covered, did you check that you are getting spark at the plugs? There's a brown with white wire on the coil also.
Also, run a 12V hot line to the fuel pump and see if it comes on.
If these two things are OK, then we know we're dealing with a control issue.
The inline fuse doesn't come from the ignition switch, it's always hot. If neither end of the wire at the inline fuse has power, I'd check the dual relay. There's a diagnostic to check it here:
http://www.wcmotors.com/personal/Fiat%2 ... agnostics/
Don't hesitate to call if you want.
Ron

[nicktheviking]

Thanks, Ron. I'm going to be splicing in a modern fuse to the brown/white wire tonight and then starting the troubleshooting from scratch... ie., air, spark, fuel. I'll follow the diagram you provided.

[nicktheviking]

Update:

I've got spark, so I think ignition is fine.

When I hooked up a test light to my fuel injectors, it is constantly on... trying to wrap my head around this one.

Any ideas?

[nicktheviking]

Finished troubleshooting--bad double relay. This also explains the fuel injectors!

Now I just need a relay... anyone got a spare?

[So Cal Mark]

the relay supplies power to the injectors, the ecu grounds them. If you have constant power to the injectors and no pulse when cranking, the relay is not the problem. The ecu needs to see a signal from the coil that the engine is turning over. The ecu grounds are on the left side of the plenum

[nicktheviking]

the relay supplies power to the injectors, the ecu grounds them. If you have constant power to the injectors and no pulse when cranking, the relay is not the problem. The ecu needs to see a signal from the coil that the engine is turning over. The ecu grounds are on the left side of the plenum

Really? Hmmm...

Well the test light, affixed to the fuel injector connector stayed solid.

According to the troubleshooting link that Ron supplied, jumping the brown/wire with the green/black wire, it diagnosed a faulty relay.

[rlux4]

Mark, wouldn't it be unlikely that the grounds on the intake plenum would cause a problem all of the sudden? I'm thinking it's a control problem because an electonic component can stop working suddenly. I admit I may be leaning this way because it's what I experienced. Assuming the grounds on the plenum are still attached, and making good contact, might it be the ECU that's not passing the ground through?
Ron

[So Cal Mark]

the whole scenario is unlikely. Odd that the ecu would fail overnight. The method that Nick is using to check current to the injectors could also be the problem. One side of the injector harness will always be hot, the other side will pulse during running/cranking as the ecu drivers ground/unground the other side. If you disconnect the inj harness and put a test light to the hot side, the light will stay on as long as the key is on

[rlux4]

I see what you mean, and I agree. (Not that you need it.) I also doubt it's the ECU, and even though I hear that dual relays rarely fail, that's the component I'm placing my bet on if replacing the bad inline fuse holder doesn't turn out to be the problem.
I suggested Nick get a noid light. I think these things are the ticket for checking out the signal to the injectors. The pulse is so fast and weak that I couldn't really use a test light or VOM for them.
Ron