AAZ Intermittent start problem

[Middle29]

It's happened four times. Turns over but won't start. AA started it once and said replace glow plugs, other mechanic said they were fine and cleaned up the main fuse. Ivejumped it off the leisure once and at the weekend managed to start after trying maybe 15 times. Now it's done it again and won't start.
So I'm after ideas of why it won't start intermittently. Other times it starts on the button. Guy by side of road hinted at fuel return when starting on a hill??

Any help appreciated as I'm in Cornwall with family
Mike

[ajsimmo]

My initial thought is glow plug relay. Either a poor connection to it or the relay itself. It's a timer relay, and puts power to the glow plugs for a predetermined time, switching them off sooner if engine is hot. Is the glow plug light on the dash working normally?

[Middle29]

thanks for the reply, funnily enough the glow plug light seems to just stay on but I might need to check that. So It's probably not operating normally I suppose but I've always been unsure if it should work as normal after an engine swap. Where is the relay located? I can check connections to it at least.
Cheers

[ajsimmo]

It depends if it was originally a diesel before the conversion to AAZ. If so, the relay should be in the black plastic box back left of the engine bay. If it's been moved, it's sometimes on the bulkhead next to black box. The operation can be checked with a test light onto a glow plug, then turn ignition on to see if (and for how long) the glow plugs are energised.

[Middle29]

Yes was a diesel. Excuse my ignorance but still learning - the old timer VW mechanic Cleaned this area up (black box on left) and mentioned there can be starting problems there, I thought he said it was a big fuse but maybe he said relay

[Middle29]

I read a post about faulty temp sender too, and a guy working nearby suggested disconnecting it. We tried that too with no effect. He did say that was with the PD engine?!? Not sure...

[ajsimmo]

The relay is right above that big fuse. It is a common failure with age, but an easy fix to just swap for a new one anyway. Part number is 171911261, google it and get one for about 20 quid.
All the temp sender does is make the relay vary the time the glow plugs are on for, as you barely need them on a hot engine. Disconnecting it makes them stay on longer so it will start better, in theory.

[Middle29]

Ok Thanks, been looking at it again today. Seems to be a lot of air in the fuel system. When turning it over tons of bubbles shoot down to the fuel pump, then return to the filter when you stop turning the engine over.
I Was going to bleed it by taking off the furthest forward banjo fitting but haven't a socket the right size!!!

I hear a good audible click coming from that black box when the ignition is turned on.

Any tips for checking fuel?? It might be me but this seems to always happen when I'm pointing downhill slightly- wondering if air seeps into the pump. Fuel lines defo need upgrading as there are joins and odd bits clipped together.

[lefty67]

Possibly air getting in where hoses connect to diesel filter, ive had this problem! Poor connection to stop solenoid, also had this problem! Wrong glow plug fuse, had this problem too! Split in rubber blanking cap on first injector, also had this problem!
All manifested in poor performance or non starting.

[ajsimmo]

Have also seen air getting in the pump driveshaft seal, which lets fuel run back to tank. Causes really bad starting, misfires for a few seconds once started, but runs fine once air purged.

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[Middle29]

Thanks for all your help gents - I've replaced fuel lines between filter and pump & added a manual primer and so far she's starting & running great. Looks like air was getting into the banjo fitting at the pump end. The fuel lines were old, cracked brittle with the wrong clips and 3 sections instead of one.. so alls well - I'm off to the beach!!!

[Middle29]

Possibly air getting in where hoses connect to diesel filter, ive had this problem! Poor connection to stop solenoid, also had this problem! Wrong glow plug fuse, had this problem too! Split in rubber blanking cap on first injector, also had this problem!
All manifested in poor performance or non starting.

As an aside an AA man once said he swapped blanking caps for bits of fuel hose with a screw in in - said it was more reliable