Trouble Shooting Help
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Trouble Shooting Help
Hello all. I need a bit of help with trouble shooting our fire company’s 1988 E350 7.3 diesel ambulance. We picked it up from paint on Friday and as we were approaching a red light, the vehicle just shut off. No puttering, backfire or anything. Upon trying to restart I noticed the "wait to start" and the other warning light that usually comes on, doesn’t. The engine will turn over but not start up. When we picked the vehicle up in TN, we had the lift pump, one of the injectors fixed and the starter replaced before bringing it back to Pittsburgh. Logic tells me that is seems to be an electronic problem but I don’t know where to start looking on a diesel. Any help trouble shooting this problem would be greatly appreciated. 
Post Fiend
Joined: Jan 2005
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You may have lost power to the fuel shutoff solenoid (FSS). If you look on the injector pump (between the V at front of engine) the Wire connection to the FSS is the one nearest to the front of the engine. With key "on" you should have 12v at the wire and also when you unplug it and pulg back on you should hear the solenoid click. Check that out.
You can also jump from a positive battery terminal to the FSS and see if the engine then starts.
You can also jump from a positive battery terminal to the FSS and see if the engine then starts.
Fleet Mechanic
Joined: Jan 2011
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From: 8600 ft in Colo
With the wait tor start light off, I'd be looking at power to the fuel shut-off solenoid. With the key on, there should be 12v to it. It's the connector toward the front, on the drivers side of the IP...
btw- You're having trouble shooting your help?
(Sorry, couldn't resist... :-)
btw- You're having trouble shooting your help?
(Sorry, couldn't resist... :-)
Fleet Mechanic
Joined: Jan 2011
Posts: 1,709
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From: 8600 ft in Colo
That pic is looking at it from the passenger side. The throttle cable connects to it on the pass side, and there are two electrical connectors on the drivers' side. The front one of those two is the one you want...
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I did not get a chance to look last night but I do have a few questions.
1. What if there is no power to the solenoid? Is there a fuse that could have blown or a relay go bad?
2. What is there is power? What would be my next steps?
1. What if there is no power to the solenoid? Is there a fuse that could have blown or a relay go bad?
2. What is there is power? What would be my next steps?
Fleet Mechanic
Joined: Jan 2011
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From: 8600 ft in Colo
You really need the wiring diagrams for your truck. I only have the wiring for the later ones, but it's likely the same...
The reason I suspect an electrical issue is that the wait to start light isn't coming on as well. On the later trucks, when the key is turned to on or start, the ignition switch supplies power to fuse K in the power distribution box, then from fuse K, to the glow plug controller, to the fuel shut-off solenoid, and the temp switch, cold idle solenoid, and cold timing advance solenoid. If that circuit is bad, it would do exactly what you're describing...
The reason I suspect an electrical issue is that the wait to start light isn't coming on as well. On the later trucks, when the key is turned to on or start, the ignition switch supplies power to fuse K in the power distribution box, then from fuse K, to the glow plug controller, to the fuel shut-off solenoid, and the temp switch, cold idle solenoid, and cold timing advance solenoid. If that circuit is bad, it would do exactly what you're describing...
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Well after checking the wire for the fuel shut off solenoid, I did not have power to the wire. So we traced the wires and found out that the wire harness from the alternator was melted into a nice mess. BINGO, there is my problem. Now I have to figure out the who, what, when, were & why this happened. I’ll keep you all posted.
Post Fiend
Joined: Nov 2005
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From: Charles Town, W bygod Va
A lot of ambulances have larger or even dual alternators installed, just something to keep in mind if it doesnt match up to wiring diagrams and other trucks/vans of the same vintage.
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Well we got our vehicle back from the repair shop last night. The problem was a few wires that got over heated and melted. So as we inspect the repairs, we notice a small amount of smoke coming from what looks to be this solenoid when the key is on and not running. I don’t know if it might have some left over diesel fuel on or in it from a bad injector that was leaking but the yellow wires get nice and hot. I don’t want to put this in service and have it catch fire. If anybody could help me out with what is this part, what does it do and should the yellow wires get hot would be greatly appreciated.
i ain't rite
Joined: Mar 2005
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From: Marlboro Mental Hospital.
that is the glow plug relay.
those yellow wires carry a lot of current to heat up the glow plugs, but they will only be hot for a few seconds. once the engine is running the power is shut off and the wires should cool off.
those yellow wires carry a lot of current to heat up the glow plugs, but they will only be hot for a few seconds. once the engine is running the power is shut off and the wires should cool off.
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