DIY Glow Plug Harness -> no "wait to start" light

sieg01

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We've made our own glow plug harness.
Basically one for the left and one for the right row.

Reason for this was that my '94 idi has a hard start when cold.
Glow plugs are new. (Beru)
Glow plug controller is new (Motocraft)
No air intrusion anymore (https://www.oilburners.net/threads/e350-idi7-3-fuel-sending-unit-air-intrusion.91338/post-1103580)
Battery cables and connectors are new. Batteries have 13.6V
IP timing is fine.

After the "wait to start" sign went off, the controller started clicking for the next 15 secs and firing up the engine was horrible.
The glow plug harness was for me the last possible source of the problem. (the female cable plugs for the glow plugs were replaced in 2019/20 because the original ones didn't keep the contact anymore)

The harnesses are 2 symmetric sets.
one main cable goes to a distributor (https://de.wikipedia.org/wiki/Federkraftklemme),
which looks like this: https://commons.wikimedia.org/wiki/File:Wago_221-413_splicing_connector_with_stranded_wire.jpg
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and from there 4 separate cables go to each glow plug.

After connecting them, we wanted to start the engine. But when turning the key to "run" position, the "wait to start" light didn't flash.
Also the controller didn't start heating the glow plugs.

All fuses are fine. The controller receives power.

When then turning the key to ignition, the engine wants to fire up.

Now, my question is: why does the controller not heat the plugs?

I am assuming that the controller measures the cable resistance and it thinks, that the engine is warm.
Can this be?
 

Farmer Rock

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Sounds like wires crossed on the relay. I've had that happen a few times.
I have to ask though, why are you using household distribution blocks like that instead of soldering a harness?

Rock
 

sieg01

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Sounds like wires crossed on the relay. I've had that happen a few times.

Thanks for the hint.
I'll check this tomorrow.

I have to ask though, why are you using household distribution blocks like that instead of soldering a harness?

Rock

I want to have easy access to every single glow plug. On this way I'll have the option to have an easier failure search.
@ least I thought so :)
 

Big Bart

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Correct the controller measures resistance so it knows when too many glow plugs have died or there is another issue like a bad wiring harness.

1) Check to see if any wires came off the controller when you worked on it. Generally the WTS light goes on for a sec, then goes off immediately if it senses the wrong resistance. You suggested it does not come on at all. Maybe when it see’s a big issue with resistance it does not come on at all, but I think it does for one second. So guessing something is not hooked up now.
2) I suggest you buy a set of glow plug wiring harnesses from classics diesel designs, members here have had good luck with them. Well made!
 

ROCK HARVEY

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I replaced my harness when I did my glow plugs last fall. I’m actually using a slightly modified glow plug harness from a 6.0 powerstroke. As for your issue, I would triple-check your connections at the glow plug controller. It sounds like the relay isn’t switching at all, which makes me think the signal wire or ground isn’t connected. Do you hear the glow plug relay (not the starter relay) clicking?
 

sieg01

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Correct the controller measures resistance so it knows when too many glow plugs have died or there is another issue like a bad wiring harness.

Thanks for the confirmation.

1) Check to see if any wires came off the controller when you worked on it. Generally the WTS light goes on for a sec, then goes off immediately if it senses the wrong resistance. You suggested it does not come on at all.

Yes, it does not come on @ all.

Maybe when it see’s a big issue with resistance it does not come on at all, but I think it does for one second. So guessing something is not hooked up now.
2) I suggest you buy a set of glow plug wiring harnesses from classics diesel designs, members here have had good luck with them. Well made!

I am not located within the US. This makes things pricy. (bank fees + shipping + customs + VAT)
I need to wait until my IP is worn out, so I can purchase a bundle. Then the additional costs are acceptable.

- snip -

I would triple-check your connections at the glow plug controller. It sounds like the relay isn’t switching at all,

Yes, it does not switch @ all.

which makes me think the signal wire or ground isn’t connected.

I will check both of it.

Do you hear the glow plug relay (not the starter relay) clicking?

No, nothing happens.

I also think/thought that the "start the controller" signal is missing.

If all looks good, I'll return the original harness to see if it will then work again.
If no - then I have a new problem,
if yes, then the problem must be related with the harness.

And - I hope we know what we're doing, as we're producing the Ullmann Power-Station ;)

Anyway - I'll be back after the upcoming test round.

Thank you!
 

sieg01

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Back again.

We've re-plugged the original harness and the "WTS" light is back on.
Controller makes also the familiar "click" when turning the key to run position.

Means, that the DIY-harness causes the WTS- failure.

Is anyone able to measure the resistance of an original harness (which is good) between controller and each single glow plug connector?
Then there are reliable figures to be compared with any other harness.

We could measure mine, but I don't trust it - at this point.

Thanks!
 

franklin2

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Those push-lock type wire connectors are not very good for high amperage connections, especially in a dirty underhood environment.
 

Selahdoor

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Those push-lock type wire connectors are not very good for high amperage connections, especially in a dirty underhood environment.
Franklin beat me to it.

You have high resistance right there in that connector.

On this way I'll have the option to have an easier failure search.
In my opinion, (Which is probably worth every penny you paid for it. LOL), you have instead, an easier POINT of failure.

Take that harness apart, and solder those connections, and try again. I'm betting your problem will be gone.
 

sieg01

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Hi @ all!

Thanks for your support and quick respond!
Sometimes - when you are experiencing some "unexpected panic" - it means a lot that one is not standing "alone in the rain". I suppose you know what I mean. :)

Ok, we sourced the problem of the "controller clicking" and hard start.
In my case, one of the "new Beru (Motocraft ZD9) glow plugs" was dead.
Lucky us, we didn't throw away all of the old ones... so one of them is back in use (AC Delco 32G).

We'll probably take the harness measurements one day and then we can source the DIY harness problem.
 
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