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Moxam
04-15-2010, 10:49 AM
Hi just wondering if anyone would know the fix for my 1994 LT1. Won't start. Will turn over but I am not hearing the fuel pump when I turn the key. If I take the purple exciter wire off the alternator and jump it to the orange power wire of the alternator I hear the fuel pump and it will start and run. Take the purple wire off it shuts down. Any ideas would be greatly appreciated.

Cheers

Paul

cbryan70
04-15-2010, 11:17 AM
kill switch?

JimN
04-15-2010, 11:21 AM
Hi just wondering if anyone would know the fix for my 1994 LT1. Won't start. Will turn over but I am not hearing the fuel pump when I turn the key. If I take the purple exciter wire off the alternator and jump it to the orange power wire of the alternator I hear the fuel pump and it will start and run. Take the purple wire off it shuts down. Any ideas would be greatly appreciated.

Cheers

Paul

Check your fuses and the fuel pump relay at the motor. Also, look at the ground wires at the rear of the motor and make sure none is loose or a terminal is broken.

east tx skier
04-15-2010, 12:57 PM
I got a pm from him earlier. It's not the kill switch.

Thrall
04-15-2010, 01:31 PM
Orange wire is the charging lead right? Elect Short in the alternator?

Thrall
04-15-2010, 01:35 PM
Seems your fuel pump relay is getting a signal from the ECM and power once you jump across the alt, so the fp relay is likely fine.
I've sent these bad photcopies of elect troubleshooting out several times in the last cpl weeks (what a coincidence I needed them in April 2004), maybe they'll help track down your problem.

JimN
04-15-2010, 01:59 PM
By 'turn the key', does he mean crank the motor or just turn the key to ON? If it's not priming when turned to ON, the checks I posted should be done. If it's not latching the relay when cranking, I'd check for spark. If the IC module isn't getting signal from the crank sensors, it won't tell the ECM to latch the fuel pump relay during crank, either. It should still prime with the key turned to ON, though. On the earlier EFI motors, the ECM sends 12V+ to latch the relay, so pin 85 or 86 will be hot only when the ECM tells it to be (I don't have my LT-1 manual in front of me). If it's 85, then 86 will be grounded.

Since energizing the purple wire causes the pump to work, the problem is on the other end. Look at the ignition switch for loose wires. If the purple wire is off or loose at the ignition switch, this will obviously show up when testing at the kill switch- no 12V with key ON. I have seen a few boats with bad terminations on the wires, too.

Moxam
04-15-2010, 02:38 PM
I will try everything above I changed the switch this morning not the problem. So I will try the above checks. Thanks to everyone who responded. I will update you on the progress. Once again thanks to those who took the time.

Cheers

Paul

JimN
04-15-2010, 02:52 PM
I will try everything above I changed the switch this morning not the problem. So I will try the above checks. Thanks to everyone who responded. I will update you on the progress. Once again thanks to those who took the time.

Cheers

Paul

Which one did you change? Did you measure 12V at the ignition switch when you turned it ON?

Thrall
04-15-2010, 04:21 PM
(I don't have my LT-1 manual in front of me). .

Jeesus Jim, I posted it for you even!:D
I believe Moxam said it cranks, but no fuel pump prime unless he jumps the alternator.

BTW, Moxam, listen to Jim....intently. He knows more about these engines than probably anyone else who's active on here. He was instrumental in getting my LT-1 up and running.

JimN
04-15-2010, 05:29 PM
Jeesus Jim, I posted it for you even!:D
I believe Moxam said it cranks, but no fuel pump prime unless he jumps the alternator.

BTW, Moxam, listen to Jim....intently. He knows more about these engines than probably anyone else who's active on here. He was instrumental in getting my LT-1 up and running.

Dang- it's not like you posted the WHOLE manual, including the wiring diagrams. Actually, the shot you posted is for the newer MEFI- if the test light is connected to B+ and the fuel pump trigger is probed while it's energized, the test light will be seeing B+ from both sides. On this one, the test light needs to be connected to a good ground and then check the relay's trigger and all of the associated wiring that should carry + voltage.

The 'no prime' issue is why I detailed it the way I did. The screws holding the wires onto the ignition switch don't always stay put and I have seen more than one fall off completely. That alone sounds logical for this one because he clearly has no B+ from the ignition tab. I think we should be uploading videos when we do certain tests, too. There must be some way to not have to deal with useless comments from outsiders, like on YouTube. With audio, I'm pretty sure a lot of things could be diagnosed more easily that with just a description. I'd listen to EngineNut- he works for Indmar.

chico
04-15-2010, 09:47 PM
They hang the system relay and the feul pump relay right below the manifold drain,I`ve seen the system relay complety corroded.

ksdaoski
04-15-2010, 10:08 PM
wheres that carb'd thread?

Moxam
04-19-2010, 10:28 AM
Well boys with your help the problem is fixed it was a dead safety switch. Wired it together works perfect.

Thanks again.

Paul

east tx skier
04-19-2010, 11:26 AM
Well boys with your help the problem is fixed it was a dead safety switch. Wired it together works perfect.

Thanks again.

Paul

I seem to recall that being the subject of my PM to you. 8p

psychobilly
04-02-2012, 09:37 AM
Well boys with your help the problem is fixed it was a dead safety switch. Wired it together works perfect.

Thanks again.

Paul

Sorry to dig up an old thread but I reckon this might be my issue too.... I need to get out there and start trouble shooting my problem. I bet it could be the connectors. I already know I have some wiring issues as my voltage gauge don't read correctly... Need to get a volt meter on it but I think I will go ahead and put a new fuel pump on her as this one is prolly 22 years old...

So if the dead man switch isn't working it kills the juice to the fuel pump?

JimN
04-02-2012, 09:49 AM
Sorry to dig up an old thread but I reckon this might be my issue too.... I need to get out there and start trouble shooting my problem. I bet it could be the connectors. I already know I have some wiring issues as my voltage gauge don't read correctly... Need to get a volt meter on it but I think I will go ahead and put a new fuel pump on her as this one is prolly 22 years old...

So if the dead man switch isn't working it kills the juice to the fuel pump?

Regardless of whether the safety switch works, or not- the fuel pump should prime for three seconds when you turn the key ON and you would be able to hear this if you open the motor cover. If you hear nothing, the first thing to check is the fuel pump relay and the trigger voltage going to it.

If the voltage gause is wrong, make sure the resistance from the ground at the dash to the battery - stud is no more than about .1 Ohms (NOT the cable terminal- ALL connections for voltage and ground should be referenced to the battery studs, not the cable terminals). Check the terminals on the ignition switch, too. If they're corroded, the voltage coming out of the switch will be lower than what's required for accessories to operate properly.

psychobilly
04-02-2012, 10:05 AM
Well it's never primed like that. It's always been, turn the key to crank, and then when you let off of it you can hear the fuel pump for three more seconds. I talked to a feller at SKIDIM and he was telling me that it was some safety feature. I can't remember how he said it was wired so I got to call him today. Seems like he was saying that one post was tied to the oil pressure and the other side to the silenoid and it wouldn't throw power to the pump until you had oil pressure and the motor was turning over.... Mine's an oldy, '91 240, BB454...

So I run a wire from the ground behind the dash to the batery box and then ohm meter from negitive post to wire to negitive block behind dash right? Sorry Jim, I'm an idiot when it comes to wire'n... Just want to be sure I read ya right. Thanks for the help bud.