I have a few issues -- please help! Fuel pump and head lights.

[wuudchuck]

Hey Guys!

It's been a while since I posted, sadly that's due to the distance between the truck and I.


We've been able to start the LMTV (1995), but the fuel pump does not get power with the switch flipped. The only way to get it started was by running a jump wire from the batteries directly to the fuel pump. It works, but it's not ideal and I'm worried about shorting out the fuel pump.


Second issue I have -- I finally sorted out how to turn on the lights, unfortunately as soon as I turned on the head lights they went on for a few seconds and then it went dark. Not the rest of the lights, just the head lights.
I tried another 15A 12v relay in it's place (slot C78 I believe) and still no lights. I plan to check with a multimeter tomorrow to see if power is going to the lamps still.



Can anyone point me into the right direction with troubleshooting these two issues?


Thanks guys!

 

[wuudchuck]

Additionally another issue I just recently discovered tonight is sometimes it hesitates to go into D from neutral. It will go into R without hesitation though.

I feel like the more this truck sits the more things mysteriously appear

 

[wuudchuck]

I mistakenly said fuel pump when I meant fuel shut off solenoid. The only way it will run is if I run the jumper to the solenoid, not the fuel pump. Hopefully that clears it up.

 

[Suprman]

You should start by going thru the power panel make sure all relays and breakers are correct ones and in the correct place. There is a guide under the cover.
Will

 

[wuudchuck]

You should start by going thru the power panel make sure all relays and breakers are correct ones and in the correct place. There is a guide under the cover.
Will

Verified them earlier -- everything looks good there. Spent about an hour reading the diagram and confirming each individual relay and breaker. I considered going to NAPA to see if they had the proper relays and breakers to just replace all of them.


I also looked through the TM's and searched for fuel solenoid and electrical systems (**** they're complicated!) but did not find my answer there either.

 

[Suprman]

Some relays require the center pin and some don't. The wire harnesses corrode and you get bad contacts. It could be a relay switch them around see if the problem moves.

 

[wuudchuck]

Some relays require the center pin and some don't. The wire harnesses corrode and you get bad contacts. It could be a relay switch them around see if the problem moves.

Will do first thing in the morning. I noticed a lot of sand when I was checking them. I'm guessing my truck has been either deployed or someone took it into some dirty water.

 

[Suprman]

Going thru water up to the power panel will cause a lot of issues over time. If the panel has corroded contacts you can clean them with a very small flat file. Once it starts does it drive?

 

[wuudchuck]

Going thru water up to the power panel will cause a lot of issues over time. If the panel has corroded contacts you can clean them with a very small flat file. Once it starts does it drive?

Oh for sure, I took it up to 55 earlier today after I got the lights working. Just don't have head lights.

It runs & drives like a charm, just won't start without the jumper lead.



Here is a link to the photo of my distro panel: http://i.imgur.com/exNwJDs.jpg

As you can see it's very very dirty. I'll clean all of it up tomorrow with rubbing alcohol or something.

 

[Suprman]

Sounds like an issue with dash power if no lights also. When you turn on the main power switch it should activate a relay for the fuel solenoid. The light switch should always have power. Do you have 12 and 24 volt at the 2 posts left side of the power panel? They are labeled.

 

[Lmtv772]

you may have a short in the instrument wiring harness, that was pretty common on the early LMTV. Check the wiring to the light switch and wiring that runs through the openings behind the dash panel.

 

[wuudchuck]

Sounds like an issue with dash power if no lights also.

All lights, including dash lights, work fine with the exception of the head lights. The head lights worked for around 2 seconds when I turned on the high beams.

When you turn on the main power switch it should activate a relay for the fuel solenoid.

Do you happen to know which relay that it will activate?

The light switch should always have power. Do you have 12 and 24 volt at the 2 posts left side of the power panel? They are labeled.

The light switch has power no problem.

I'll check with a multimeter to see if it's getting 12 and 24v respectively here shortly and report back

you may have a short in the instrument wiring harness, that was pretty common on the early LMTV. Check the wiring to the light switch and wiring that runs through the openings behind the dash panel.

I guess today is a gremlin hunting day! I'll see if I can follow all wires to see if there's a short somewhere. I did notice a loose wire behind the front passenger seat, I assume that handled the chemical detector.

Also lmtv772, you're the one who commented on my YT video Just noticed that.

 

[Lmtv772]

Welcome, nice to see you again wuudchuck

also check all the wiring that goes to the front lights and see if there is condensation in the turn signal lights. I had some strange feedback to the dash from a shortened out turn signal assembly.

 

[wuudchuck]

So I went through everything again today. I used a multimeter on the terminal posts on the electric panel....which may be the source of my issues. Both the headlights and the fuel shutoff solenoid.


Both register at 24v, I hooked up the batteries based on a picture posted somewhere on the forum here (I can't seem to find it now for reference...). I will keep searching, I will also post pictures on how I have the batteries hooked up. Hopefully someone can tell me what I did wrong.



Edit: Another issue popped up today as well, the cab will not lower all the way down now. The cab latch is also stuck in the closed position, which partially is why it won't go down all the way.

Is this latch operated via an air valve?

 

[Suprman]

The battery diagram is on the inside of the cover.

 

[wuudchuck]

The battery diagram is on the inside of the cover.

yeah, unfortunately not so much with mine. There is no diagram on mine. Mine was one of the trucks repainted from woodland to desert and with that all of the labels were painted over, removed or weathered.


They're wired up to the diagram specs as best as we could translate, but it does not account for routing of the wiring so things may be in different locations. It's hard to explain via typing, so I'll show a picture tomorrow.

 

[Webrep]

Just found this earlier tonight myself

 

[wuudchuck]

View attachment 598761Just found this earlier tonight myself

Thank you, yeah that's the one we were following tonight. For some reason I had a ground running to battery #3's negative post. All of the other wires appear to be correct with the exception of that.

I also was unsure with the cutoff switch -- is that the in-cab switch? or is there a switch I'm missing somewhere?

 

[wuudchuck]

Okay we now have 12v and 24v!
Had some cables mixed up.


Does anyone know which relay runs the fuel cutoff solenoid? I went to NAPA here in town and they did not have any of the relays or breakers that the truck needs, so I'll have to source them from another store.


Thanks!

 

[Suprman]

The relays are standard bosch style ones napa has the 12v ones at least. Any car stereo install shop will also have the 12v ones. The 24v ones can be found online inexpensively in bulk.
Will