Cdti intermittent non start

[Eddiebassman]

Hi. My mk1 75 cdti has on two occasions turned over but wouldn’t start. No attempt to fire, no struggling or spluttering, just the start turning over.
The first time I tried it a few times over a couple of hours with no success, then unplugged the fuel filter housing, plugged back in, then the car started.
The second time this happened, it was going dark so I used my wife’s car, and left until the morning. However the car just started, which has cast doubt on whether unplugging and plugging back in the connection to the fuel pump on top of the filter made any difference.

A couple of things happened recently, OSf wheel arch was ripped off along with brake pad wiring which I joined together and I’ve had a remap by big russ. I can’t imagine that any of these made any difference, but but full disclosure thought worth mentioning. Can anyone suggest what could be the issue?


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[trikey]

I guess at a low fuel pressure issue from a failing pump.

[Eddiebassman]

I thought that, but could that theoretically rectify itself if left overnight? That’s the bit that threw me. So is the bit that screws onto fuel filter a pump as it seems small. I’ve ordered another one off here as it was only £15 anyway. So figured it would be worth a go.


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[trikey]

The pump is in the tank, and there can be one under the bonnet near the bulkhead if you have an early car.

It’s a filter that screws on to the housing, worth replacing if you haven’t done it.

If you only have a single pump system I’d look elsewhere for the issue as the single pumps rarely fail.

Maybe worth a trip back to Russ to see what T4 says.

[Eddiebassman]

Yeah I’m planning some work with Russ anyway, but I know how intermittent faults are like to trace as I’ve worked in dealerships and can only assume they weren’t as good in 2004!

I’ll swap the housing anyway, I may as well. Mines a mk1, just before the change.


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[Eddiebassman]

Wouldn’t start again today. On the advice of big russ, I lightly tapped the under bonnet fuel pump and it came back to life.

Looks like you was bang on there trikey

Thanks


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[Arctic]

Hi Eddie.
Only fit a pierburg UBP or at least a good used one, aftermarket pumps fail after a short while.

You need to make sure it have a good flow rate, i maybe able to help you out drop me a PM

https://youtu.be/MikZPHxCUww

[bl52krz]

Originally Posted by Eddiebassman

Wouldn’t start again today. On the advice of big russ, I lightly tapped the under bonnet fuel pump and it came back to life.

Looks like you was bang on there trikey

Thanks


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Take the plug off the top of the ubp and put some Vaseline on the terminals, and then put the plug back on and off a couple of times. Might do the job. Did mine and it was ok.

[COLVERT]

Originally Posted by Eddiebassman

Wouldn’t start again today. On the advice of big russ, I lightly tapped the under bonnet fuel pump and it came back to life.

Looks like you was bang on there trikey

Thanks


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Hi there Eddie. You didn't tell us what cured it.---

[Arctic]

Hi Jon.
he tapped the UBP therefore maybe like a lot of members he carries a screwdriver in the boot to tap the UBP if it's working intermittently, either until it no longer works, or it's changed for a good working pierburg pump or a new one.