1990 d150 no guages no crank!! Need help please

[Lucasville45]

My brother has a 1990 d150 was driving and the windshield wipers came on and then the truck just died while he was moving.luckily he was able to coast it in his complex and its been sitting since then about a week now.The truck has power to heater,headlights, taillights because they are still coming on but no guages or windshield wipers plus you can't hear the fuel pump kicking on and then the most important thing no crank at all.we had the battery alternator and starter checked and they were all good.we was looking again at the wiring harness and noticed a huge problem that wires were burnt and shorting in the manifold I guess he didn't have them secured good.well anyways he repaired the wires got another asd relay to try that and still nothing.we checked the fuses all of them look good but there is no box under the hood for fuses just the ecm.sorry we aint mechanics but try our best to troubleshoot before taking to garage because he's disabled and on a fixed income so money is tight and a new ecm is alot to him.any help would be aprecciated.thanks

 

[pacofortacos]

Did you check all of the fuse links - they look like wire.
AT least back in the day, mopar used fuse links quite a bit - BUT I am not 100% sure that the trucks did in 1990 or not.

 

[Lucasville45]

I was told to check those too but have no idea how or where to start.i guess it's looking like he will have to take it to a shop.we did try to jump it at the starter and it did crank but of course without ignition or fuel having power we knew it wouldn't start but did give us hope that the truck atleast cranked.would a dead ecm cause it to not have power to crank but still have power for headlights and heater and etc?thanks for your reply and anything else we could try.

 

[pacofortacos]

They are wires usually near the battery + terminal - they will usually look good from the outside even when open.
Usually I would grab each on and give it a medium pull - if it stretches any then it is open circuit and you should be able to pull it apart.
If they just go tight then solid, they are ok.

There used to be several and several different gauges.

You really need a wiring diagram and voltmeter to test it all - at the very least a test light and really know what you are looking for or diagram.

 

[pacofortacos]

Do you have battery voltage to the starter relay?

 

[Lucasville45]

Thank you I will give it a look and see if I can locate the ones you described.I did notice a few wires coming from the power terminal with what looked like rubber tubing over them.thanks again for your help

 

[Lucasville45]

Do you have battery voltage to the starter relay?

I will have to get a meter to check I only got a cheap test light I bought for fuses.my knowledge is limited especially with wiring.thanks

 

[pacofortacos]

It's hard to troubleshoot electrical over the web. haha

You should have a constant 12 volts at the starter relay - I would start there.

A test light would work for voltage testing of the 12 volt system.

Key off, there should be 12 volts on one terminal of the starter relay - we can go from there.

 

[Lucasville45]

Yeah I tested the wires of the starter relay and all but one had a strong light from the cheap test light I had..the orange wire was dim and like real weak.

 

[B250]

I agree with pacofortacos - start by checking ALL the fuses and make sure they are not corroded in their sockets. Fusible links are hard to locate as they look like normal wires, but they are designed to only blow at high loads (typically on headlight or starter/alternator circuits).

Try the key on-off procedure to see if there are flash codes on the dashboard. If there are, this means the computer is 'alive and kicking' so is operational at least.

I had a problem with my van when driving in heavy rain - water was forced under the hood lip and shorted out the ECU, but I solved it by fixing a rubber seal at the front edge of the hood to keep the water out.

I've attached some wiring diagrams that are for the 1991 model year, but the 1990 year seems the same and indeed my 1991 van seems to have a 1990 ECU installed

You really need to get a multimeter - Harbor Freight Tools have a useful one for about $7 - then you can measure voltages at the various connections in the circuits.

My experience over the past 35 years is that 9/10 it is an electrical fault and 9/10 of those it is corroded connections or shorted wires against the bodywork

 

[B250]

Update - From the wiring diagram above, as long as the neutral switch is closing on the transmission (ie. grounding) and the starter relay is good, then the ECU has no effect on the operation of the starter motor. If the starter motor won't engage in such situations it suggests you may have a problem with your ignition switch or the power supply to it.

Luckily the ECU on these vehicles was pretty basic by modern standards and many of the sensor inputs can be bypassed to keep it on the road.

 

[Lucasville45]

Thank you for the help and diagrams.i will get a multimeter and go that route .This rats nest of wires definitely needs to be gone through and retaped.

 

[Lucasville45]

Thanks for the help

 

[B250]

I've located some wiring diagrams for your model year which show the fusible links. I also remember a large 'bullet' type plug near the battery which could have corroded/worked loose. It struck me as not a very good way to connect two main power cables together.

Strange electrical things happen with my B250 now and then - especially going over bumps - so there must be something loose somewhere, but I can live with it as it doesn't affect the running of the van.

 

[B250]

I could only attach 5 files to my last message - here's the other two