ABF on K-jet - setting up & troubleshooting? Fixed and MOT'd!!!

Hi
Do a compression check.

 

have you ever had it on a proper gas tester? i cant tune mine by ear and it seems to idle the same over a huge range

 

Yes, I was thinking this might be a good step. The engine in general seems to have very good compression (very hard to turn by hand) and doesn't loose any oil, water or smoke or anything but you never know.

No, wish I had a gas tester to be honest - something for the Christmas wish list I think. It's difficult to get it on a gas tester as it won't drive far enough to get to the local MOT place hence trying to set it up DIY style!

 

If it's running a bit hot, just make sure you're checking the timing at the right engine speed, and make sure you haven't got an airlock in the cooling system.

 

Mike - yes, the timing was set at idle and the cooling system should be fine but I think it's worth a flush out anyway as I expect it'll be full of rusty water now from circultating the engine for a while. I did bleed it properly when I put the water in the first time round, the thermostat is fine and I think the fan used to come on ok too.

Rubjonny - Good point on the fan, I know it definitely comes on at both speeds if I short the wiring appropriately so it's not that. I will whip out the fan switch and do my usual test of boiling it on the stove in a pan of water connected up to a multimeter - my wife always finds this very amusing!

Fuel starvation does seem likely for the symptoms I agree, was hoping it'd come right with the WUR and control pressure set but it seems not. The lift pump is new and definitely running as you can hear it with the car running if you put your ear close enough. The main pump is definitely running and was giving me around 5 bar system pressure at the metering head at idle which should be enough surely?

The wiring to the lift pump, although a little ropey looking definitely works and doesn't get warm anymore with the engine running so perhaps the old lift pump was knackered causing that. I will look into replacing the wiring anyway.

Perhaps worth looking at changing the fuel filter? I know the accumulator is ok as from the pressure gauge I could see it held good pressure long after the car was turned off, and hot and cold starts are no problem either.

PS. I was hoping you'd see this thread as you are one of the forum's premier troubleshooters!

Thanks again for all the help everyone, hopefully we can crack this - beers are on me if we get it running properly!

 

Stu

Its probably worth cahnging the fuel filter not too expensive and worth it for peace of mind. Can you get a multi meter on the fuel pump wiring and see what the volatge is there and see what the drop is like.

 

You still havent checked the injectors!

 

Hi Jamie - yes, good plan - we picked up a new fuel filter today so will try swapping that out soon. Will also check out the pump wiring with a multimeter and replace as necessary with some decent stuff.

Yes, I know, good suggestion and it's on the 'to do before I push the car off a cliff' list

Anymore ideas?

 

Hi All,

Today's update - did a little bit more troubleshooting on the car.

Firstly I tried removing the metering head bolt with the little filter in and swapping it for a standard bolt. This seemed to make the car run a little better when revved stationary, less of a pinking noise at higher revs but it still showed the same problems when trying to drive it.

Next we looked at the fuel pump relay. It's in position two in the fuse box on this car, unlike my other later '91 model, seems a different fuse box on the earlier car without the hazard warning on the steering column? The relay looks fine although it is missing it's lid, what number should it be though in case we need a replacement?

Tried bypassing the relay with a piece of wire just in case that helped... it didn't!

Next we inspected the fuel pump wiring under the car, this looks to be in good order and if disconnected as Rubjonny suggested you can just hear the lift pump prime so that is definitely working.

After that we connected the multimeter to the wiring near the lift pump (with the wiring still connected) and the turned the ignition on. The meter shoots up to about 9.5v while the pump primes and then back down again. Testing the voltage at the battery it is more like 12.5v with the engine off so a 3v drop there.

Doing the same test with the engine running, the voltage at the pump wiring is around 11.3v, whereas at the battery we see 13.4v, so a voltage drop of around 2 volts here.

What voltage should we have at the pump wiring with the engine running? I would have thought closer to the alternator voltage? Would this voltage drop account for the apparent fuel starvation?

We tested the voltage at the fuel pump relay, with the enging running, and that is 13.4v as you'd expect so it seems to have quite a voltage drop from the fuse box to the rear of the car where the pump is mounted.

Tomorrow we are going to look at the fuel filter and replacing the fuel pump wiring to see if we can eliminate the voltage drop. Does anyone know where the fuel pumps get their earth from? Is it one of the wires in the loom or a connector direct to the car body somewhere?

Thanks for reading!

 

Stu i think the earth comes from the fusebox. the 13.4 volts at the fusebox is that the input or output side of the relay ?

 

voltage drop does seem a bit hefty...you make up a temp relayed harness to see if things improve

 

Still Havent Checked The Injectors!

 

Hmm... not sure to be honest Jamie, I measured between earth and the left hand side of the relay as you look at it. Will double check today. Which is the input and which is the output side and will it be different, I assume you mean to check if there is voltage drop across the relay?

Yes, that's what I was thinking - bypass the pump wiring and feed it straight from the battery as a test to see what voltage we get then and if it improves the running issues.

I also intend to test the pump voltage on my other (fully working!) 16v to see how it compares, can't do it yet though as I need the car to work for an airport run in a couple of hours and don't want to take it apart and break it!

I know! I think we keep trying everything else first as it's tricky / a fire hazard to test them but you're right, we do need to rule out the injectors as a possible problem. Will hopefully be able to test them today.

Hi - I tried both, with the relay in place and with a wire jumping it instead, pump voltage remained the same at about 11.3v with the engine running - this is why I thought the relay was probably ok. Thanks for the relay info above, much appreciated.

Hopefully report back with some progress later on these tests, nice day for it so I'm trying to keep a positive attitude towards the car rather than thinking of torching it...

 

http://www.clubgti.com/forum/showthread.php?t=161010&highlight=relay

i posted that thread a while back..basicly a relay kit for the fuel pump which should be easy enough to knock up

i dunno if it we what causing your prob...but surley batt voltage would ideal and wouldnt hurt things?

 

Cheers - will look into it, basically like an uprated headlamp loom but for the fuel pump - we could probably do wth something like that for testing purposes at least.


Right, today's progress. Firstly fitted a new fuel filter and investigated the wiring to the fuel pump under the car, all fine and the new filter was quite straightforward to fit.

Next we sorted the wiring connector by the lift pump by replacing it and re-terminating all the wires correctly. After this we did some multimeter testing as follows.

Battery voltage - 12.5v (engine off)
At pump connections with ignition on (engine off) - 11.3v

Battery voltage - 13.6v (engine running)
At pump connections with ignition on (engine running) - 11.8v

So, the voltage drop was a little less than before but nothing special. We suspected an earth fault and sure enough if we test from the red/yellow wire at the pump connector to earth we get 12.5v, and if we test the brown (earth wire) to earth... 0.9v!

That means there appears to be an earth fault on the circuit as the total voltage between those two wires appears to be close to battery voltage with the engine running, some is leaking to earth.

We tried earthing the brown wire in the connector straight to the body of the car, this obviously removed the volt drop to earth at the rear of the car but still only gave around 12.5v at the pump. That said, the car did seem to pull better but still pinks badly at higher revs.

We started trying to trace the wires back to the fusebox and released the fuse box to find loads of spare connectors not connected anywhere, lots of dodgy fixes to wires, taped up connectors and scotchlock things

We can trace the brown wire back to the fuse box earth, that looks ok. The red / yellow wire seems to joint into a red / white wire which goes off through the bulkhead, presumably to the ECU. I took a few pics which I'll post up later.

Any ideas on fault finding from this point - we want full voltage at the pump!

Jamie - the pump relay has battery voltage or thereabouts at both sides with the engine running if that's any help, so the voltage is dropped from there to the pump connections.

Help please!

 

Voltage drop at the fuel pump is normal i believe. I seem to remember TSR doing something with Ian B's car to try and maximise it's performance. Or at least i do remember it being mentioned when i was in TSR many years ago.
Have you still not checked the injectors? Have you swapped the dizzy for your known good one?