Fuel Pump Relay and Engine problems

[spnracing]

OK, in nothing exotic - just my shed of Golf.

FUEL PUMP DETAILS:

Symptoms:

I have a Mk1 Golf GTi race car. In qualifying last weekend (in front of BBC Top Gear camera car, race to be shown next Sunday night) the car stopped dead.

I checked everything and there was no fuel.

Looked at the relay connections and found the following when looking at the relay from passenger foot well;

Left most wire is constant live feed - OK
Lower wire is switched live feed - OK
Middle wire is earth - OK?
Upper wire is switched live feed - OK
Right most wire (87) is live feed to pump - NOT OK.

I replaced the relay with another - no change, 87 still didn't go positive, no power to pump.

In desperation to start the race I wired the pump up to the battery switch. This caused the pump to kick in but it kept going - it didn't just stop once it primed. Did the green flag lap (slow) OK, lined up behind Richard Hammond in the the BBC camera car but as soon as the lights went green the car kangarooed forward and I had to stop by the side of the track. This ended my hopes of a few laps ahead of Richard and on prime time TV. I was not happy.

The temperature gauge light was flashing and the rev counter was going mad - suggesting an electrical fault?

Investigated further at home. Tried several relays, none of them get power to the right most connection out of ther back of the relay (87) which feeds the fuel pump.

If I bridge the two connections (like the previous post) or wire the pump up to the battery then the pump runs continuously - it doesn't prime and stop. The engine will then start but I'm sure the electrical misfire will happen under load again. (This is now difficult to check/test with a non-road legal car.)

So the questions;

Should the right most wire (87) be the positive feed to the pump? I assume so.

What would stop this becoming postive other than a blown relay? I've tried three that should all have been OK.

Why does the pump run continuously and not stop whirring once the system is primed? Is that because I've bodged the wiring?

Could it be the fuel pump at fault? I haven't tried replacing it since the problem appears to be the lack of power to it - i.e. electrical.

Any help greatly appreciated. I have other (engine) problems with the car but have to sort out the fuel problem first.

ENGINE PROBLEM

I've had new very expensive forged pistons fitted and a complete refresh. Unfortunately because of a timing 'mis-understanding' we ran the car at a Snetterton track day last Wednesday with way too much advance - maybe 10 laps at most. This caused massive detonation, damage to the head/valves and a head gasket failure.

We fixed all this before the race weekend but now although the engine starts and runs fine, I have low compression (and getting lower) in all four cylinders. This started in cylinders 2 and 3. The other symptom is that the catch tank fills with oil after only a lap or so!!!

So its almost like the piston rings haven't sealed for some reason. Surely the detonation can't have caused this? Cylinders 1 and 4 WERE OK and detoriated during my vain attempts to start the race - when the timing problem had been fixed. I assume its another engine out job but has anyone any ideas what might have happened?

[Incorrigible]

Oil could be head gasket too, would also explain the lack of compression, How hot did it get ?? heads do warp (hig in the middle low at the outside) this way, Also suspect this due to compression going down on 2 and 3 cylinders

Of course the oil could be coming from a presurised sump as you suspect but either way the heads got to come off and check the head for flat and have a good inspection of the gasket

[350matt]

Its possible you've yielded the piston rings or slightly deformed the top of the piston so distorting the ring groove due to the big temperatures, but I'd suspect a tweaked head is more likely. Either way the head has to come off for inspection. you could also try the compression test with and without oil, if you take a measurement as normal then pump a little engine oil into the cylinder and repeat the pressure measurement. If it goes up you have a piston / ring problem if not then its head / valve seats

as to your electrical problem I'd start from scratch with the wiring as that always works for me.

Matt

[danhay]

Regarding your electrical problem...

The relay is there to act as a higher current switch that acts upon a signal from a smaller switch or switches. E.g. when you turn the ignition key, it sends power to the solenoid within the relay that causes it to send power to the fuel pump.

It sounds to me like it could be a problem with the circuit between the ignition switch and the relay?

[deltaf]

What management system are you running pete?

ps the electrical conns to the relay (k jetronic only) are as follows.

1=connection 1 on the coil
15= connection 15 on the coil
30= +12volts continuous feed
31=ground connection
87= fuel pump feed

Let me know if theres more info you need (if this is ok )


>> Edited by deltaf on Wednesday 14th July 21:36

[spnracing]

Thanks for the info everyone.

The fuel pump problem frustratingly disappeared after two evenings of pushing wires around and checking connections. I have thus no idea what it was and it will almost certainly re-occur on the start line at a circuit somewhere in the UK in the near future.

Yes, looks like the engine will have to come out. I re-used the head bolts which was a bad idea, re-torquing them after a few laps DIDN'T change the compression though suggesting rings rather than gasket? I'll find out soon enough anyway.

The 'management' system is bog standard KJET, Group One doesn't allow any other sensors that those that exist so I can't use 2D/3D mapping.

Thanks again everyone. One of these days (years) my car will manage to finish a race.

[deltaf]

Regarding the head bolts; it may be prudent to invest in some ARP head studs as these can be reused several times without any problems and are infinitely more capable than the OE bolts.

Regards deltaf

[weed]

You have a dodgy circuit, as disturbing the wires has apparently revealed.
Best to rewire or the problem and or thoughts of the problem are going to mess with your track craft.
m