P38 cold start issues

wammers · Jul 6, 2020

bionicbob said:
on mine they have used the blue/white and scotch locked into a red/white

I have hot start on my P38 only one wire is cut and linked through hot start. There is obviously a power feed and ground to hot start. Can't think why two separate coded wires are joined together. The hot start tells the ECU the engine is cold so the ECU switches on glow plugs. Ok my bad, look for a wire that is Grey/blue that is the feed from ECU temp sensor to ECU. It is that one that is cut a connected to hot start. Not the one i said before. But you maybe best to disconnect hot start and repair the wires. It is screwing something up. You may even get a dash temp gauge back working.

bionicbob · Jul 6, 2020

wammers said:
I have hot start on my P38 only one wire is cut and linked through hot start. There is obviously a power feed and ground to hot start. Can't think why two separate coded wires are joined together. The hot start tells the ECU the engine is cold so the ECU switches on glow plugs.

bionicbob · Jul 6, 2020

the red/white as been used to power it

wammers · Jul 6, 2020

bionicbob said:
the red/white as been used to power it

There should be a power feed and ground that is a given. But it should also have the feed from the ECU temp sensor cut and joined into it that way is intercepts the sensor signal and tells the ECU the engine is cold the ECU then sets cold start fuel and switches the glow plugs on.

wammers · Jul 6, 2020

As said the hot start may not be switching the plugs on for long enough or the connections to the plugs maybe slack giving reduced power to them. You will have to check it. Sorry about wiring cock up i am trying to do several things at once.

bionicbob · Jul 6, 2020

wammers said:
There should be a power feed and ground that is a given. But it should also have the feed from the ECU temp sensor cut and joined into it that way is intercepts the sensor signal and tells the ECU the engine is cold the ECU then sets cold start fuel and switches the glow plugs on.

yes they have used the blue/white wire

Datatek · Jul 6, 2020

bionicbob said:
well it starts every flick of the key while hot will see in morning when cold

Some hot start mods can disable the ECU temperature sensor when they go wrong and prevent correct operation of the glow plugs

bionicbob · Jul 6, 2020

Datatek said:
Some hot start mods can disable the ECU temperature sensor when they go wrong and prevent correct operation of the glow plugs

it is starting fine with out it when warm

Datatek · Jul 6, 2020

bionicbob said:
it is starting fine with out it when warm

That may mean the sensor is duff so the ECU is using the cold start settings which is the same thing the Hot Start mod does.

bionicbob · Jul 6, 2020

Datatek said:
That may mean the sensor is duff so the ECU is using the cold start settings which is the same thing the Hot Start mod does.

dosnt put the heater light on when warm even tho gauge isnt moving

Datatek · Jul 6, 2020

bionicbob said:
dosnt put the heater light on when warm even tho gauge isnt moving

Forget the gauge, it has nothing to do with the engine ECU, glow plugs or anything else, it's a stand alone device.

bionicbob · Jul 6, 2020

Datatek said:
Forget the gauge, it has nothing to do with the engine ECU, glow plugs or anything else, it's a stand alone device.

when i warm it up and restart it no heater light now

Datatek · Jul 6, 2020

bionicbob said:
when i warm it up and restart it no heater light now

So the temperature sensor for the ECU may be working, you will know when you get your Nanocom.

bionicbob · Jul 6, 2020

Datatek said:
So the temperature sensor for the ECU may be working, you will know when you get your Nanocom.

will see how it starts in the morning when cold

wammers · Jul 6, 2020

bionicbob said:
will see how it starts in the morning when cold

Have you checked the glow plug connections to the glow plug relay?

bionicbob · Jul 6, 2020

wammers said:
Have you checked the glow plug connections to the glow plug relay?

Will try that tomorrow but like I said earlier may have found a fuel leak which is why it takes 3 or for atemps to start in a morning

wammers · Jul 6, 2020

bionicbob said:
Will try that tomorrow but like I said earlier may have found a fuel leak which is why it takes 3 or for atemps to start in a morning

When the glows are active on cold start the fuel lift pump runs whilst the glows are lit. Fuel cant really run out of the injection pump to below the level of the pressure head inlet.

bionicbob · Jul 6, 2020

wammers said:
When the glows are active on cold start the fuel lift pump runs whilst the glows are lit. Fuel cant really run out of the injection pump to below the level of the pressure head inlet.

Notmaly in a morning give it one heat and it fires then just turns over the second and third heat just turns over untill I try a forth time then fine all day

Grrrrrr · Jul 6, 2020

bionicbob said:
Notmaly in a morning give it one heat and it fires then just turns over the second and third heat just turns over untill I try a forth time then fine all day

My vote is fix the fuel leak and then test again. Beru glow plugs make a big difference. Expensive but worth it.

wammers · Jul 6, 2020

bionicbob said:
Notmaly in a morning give it one heat and it fires then just turns over the second and third heat just turns over untill I try a forth time then fine all day

Still sounds like plugs.But have you checked the lift pump?

P38 cold start issues

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