Thump the dash to get it to start... 7.3 PSD E350

[Bikersmurf]

I've got an intermittent crank/start issue. I've got a 97 Crestline Ambulance, 7.3 PSD, north of 325,000 kms (discovered Odometer didn't work after buying). Once in a while, turn the key, wait for 'wait to start to go out', turn to crank position and nothing happens. Thump the dash above the Speedo on drivers side and then she'll crank instantly (if holding key in crank position) or when I turn to crank again.

It was doing it before I replaced the original, and dead, alternator. I thought the problem was solved until the other day, a few weeks after, when their was a momentary pause before it cranked, and then today it needed a thump 3 out of 5 times I started it. When it works, I can shut it off and restart it, but after sitting it acts up.

Plan so far
1) it needs a fuel bowl 'rebuild' and I plan to also replace filter... Their are fuel leaks in the valley, and replacing all the orings and looking for anything else leaking at the same time. Water in fuel light is on before it starts, and pulling the drain lever hasn't changed anything.

2) open up the dash and figure out why the odometer isn't working.

3) look for loose conections behind the dash before it leaves me stuck.


Any tips, pointers or things to look for or check?

 

[thedjjack]

Shot in the dark but next time thump the shifter maybe the N/P switch is going out? Not sure were that is on the newer computer controlled trans...

 

[Bikersmurf]

Moving the stickshift around makes no difference, but that doesn't mean it's not the problem.

BTW, it runs very well, doesnt smoke a bit, has lots of power to move the 8500 lb rig. I thought it was water in the fuel, but hitting the dash shouldn't change that.

Thanks, keepnthe ideas coming.

 

[UK4X4]

sounds like the ignition switch contacts are dying, as the starter relay is usually under the hood,,,

You usually only have two things on the start circuit.

Switch- relay - starter

Auto tran may add an interlock to that operation.....switch-interlock-relay-starter

Vehicle wiring to me is usually fraught with issues, I usually just end up adding a new wire rather than try and track down that one loose connection.

 

[gggplaya]

Because it's an ambulance, that means it was hacked into by an upfitter. A common thing to do is power up other circuits with a relay, whose coil is fed from the ignition circuit. Personally i think it's a big no-no to splice directly into the ignition switch wiring, rather i like to tap into another circuit which starts after a relay like the radio circuit. Peoples lives don't depend on the driver having a radio, but they do if the truck doesn't start.

Most likely someone made a splice directly on the ignition wire. I'd follow the wire and look for an aftermarket buttsplice. Investigate there.

 

[Bikersmurf]

I think wiring or a relay is most likely. I'll look for things spliced into it, we seem to have ignition, just not the crank option. Are there any things that are disabled when the engine is cranking (stock or ambulance)?


If it were a dying ignition switch, wouldn't cycling the switch a bunch of times change te result? It doesn't seem to mater if you turn it on and off 20 times... Hold it to the on position, thump the dash above the speedometer cluster, and she cranks instantly. I'm not ruling anything out, just trying to figure out where to start looking... There's a ridiculous amount of wiring in this ambulance to sort through.

I apreciate the input all the input. Although I know Fj40s intimately, an E350 diesel is a big lurning curve... And I'm 23 years ahead on Fj40 Landcruisers.

 

[Bikersmurf]

Is there anything related to the Diesel system, ie computer, that would relate to starting... Sensors, wires, relays, fuel heaters?

 

[Acheateaux]

Does it start in neutral?

 

[Bikersmurf]

Haven't tried neutral, but that's a thought.

I pulled apart all the upper and lower dash... Fixed the odometer (at least for now) by moving the worm gear on the odometer motor. The tip of the gear broke off so it wasn't engaging the other gear.

I tugged, pulled, poked, every wire, relay, connection I could find. All to no avail, nothing
Are a difference. I did find there is a relay, related to the start circuit behind the radio...

But... That doesn't seem to be the problem. When investigating more thoroughly I found the ignition switch is stiff and sometimes doesn't turn far enough... I'm hoping it's that simple, firmer grip on the part around th key and it cranks.

 

[Bikersmurf]

If that's the fix, I kinda feel like a fool... Problem with intermittent problems is they are very hard to test... And almost impossible to be sure they're fixed.

 

[r_w]

Yup. Intermittent electrical problems are maddening.

 

[GR8ADV]

If the vehicle is not dying on its own when underway u can rule out the switch itself and move downstream from there.

 

[Bikersmurf]

I'm thinking mechanical component of inginton, not allowing switch to turn far enough to crank. When I have a firm grip and turned harder, it has cranked every time... So far. Might not be an electrical problem... Just a truck has 15,000 hrs problem.

 

[Bikersmurf]

Fuel bowl is rebuilt and reinstalled. No water in fuel bowl.

But the problem has recurred...

It was not that the switch wasn't turning far enough. Back to a thump on the dash to have it crank.

Does anyone know what the relay under the dash at the back left corner of the radio is for (97 E350 with 7.3 PSD... ambulance)? One of the times it didn't crank until after I waited a bit, I heard a click from the relay, and then the starter kicked in and it flashed up.

 

[philos]

this may or may not help you out...