C3 2.0 RT engine - fuel pump relay issue

audimanur · 03-11-15, 08:35 PM

Hi there, I have a very annoying fuel pump relay that continues to click in and out like a nutter. Car still runs, but it is jerky obviously. It is also having a huge effect on the idle control.

Tried a new relay, didn't cure.

I cannot find what is causing the relay to cut in and out. Voltages and earths are all ok. But something is pulsing it.

Does anyone have a wiring diagram for K Jetronic? NOT KE! I cannot find any accurate info.

TIA

msh · 04-11-15, 12:09 AM

Fuel injection type this time doesn't matter - it's ignition control module which controls fuel pump relay, and it's the same hella ignition control module for both K-jetronic and KE-jetronic. If you're really sure there's nothing wrong with wiring and relay, then next step is ignition control unit...

audimanur · 04-11-15, 07:22 AM

Well, that is why I wanted a wiring diagram to test correctly.
It must be getting the wrong duty cycle/hall sender signal from the ign. Module.
Also, where is the module? I have hunted everywhere for it!

ovalking · 04-11-15, 01:27 PM

Quote:

Originally Posted by audimanur

Well, that is why I wanted a wiring diagram to test correctly.
It must be getting the wrong duty cycle/hall sender signal from the ign. Module.
Also, where is the module? I have hunted everywhere for it!

The Haynes manual says it is either under the windscreen near the wiper mech or in the passenger's footwell.
In my (RHD) car it is in the driver's footwell just in front of the door. I've removed a panel enough to see it is there, but not worked out how to gain full access yet!

How does the car run if you bypass the fuel pump relay? i.e. put a jumper wire across the 2 big sockets.

audimanur · 05-11-15, 08:22 AM

It runs okish with pump relay bridged, but I don't like the safety, or lack of, driving like that. For the time being I have disconnected isv and raised idle speed up. It stalls a couple of times when cold but is fine after 1 min of running. Doesn't stop the fuel pump cutting in and out very quickly tho! But at least people don't think I'm trying to race them at every junction!!
I have ordered a replacement ignition module and will see if I can hunt the location of it! Cheers for the heads up on its location. I will report back

The pump relay must receive a duty cycle feed from ignition module, so that it can control the isv and also the Rev limit function. There is a duty cycle on the relay pin, but I have no idea if it's correct or not. And I'm not really sure how it controls the function. Would love a wiring diagram to cure my curiosity!! Lol

msh · 05-11-15, 06:43 PM

Quote:

Originally Posted by audimanur

It must be getting the wrong duty cycle/hall sender signal from the ign. Module.

What, relay? There's basic relay which is just getting power to energize coil, nothing more.

audimanur · 05-11-15, 09:22 PM

The fuel pump relay isn't a basic relay. It controls rev limiter/idle control. There is a microprocessor on the board inside.
This is why it is hard to diagnose with the correct info for the car

audimanur · 09-12-15, 01:13 PM

OK, so I learnt a bit more once I actually found the idle control relay.......
It is located in drivers side kick well, behind a plastic protector alongside the ign. amplifier.

After testing wiring, I couldn't find anything wrong with the wiring other than the feed from fuel pump relay going. I tried a replacement idle control relay (262) and it made no difference.

I then went back to testing the fuel pump relay.

The issue had become worse and it turns out the small pin on the fuel pump relay only had a constant 10.5-10.8 volts on it. This comes direct from the ignition coil and the electronics in the fuel pump relay monitor this to allow relay to stay energised. I tested the voltage on the negative side of the coil and it also had the low 10.8v. I took the wires off the coil and found the resistance was higher than expected. It just so happened I had a brand new genuine coil sat on my shelf destined for my UR, its 99% the same. Checked the resistance which was lower and within tolerance. So I fitted it and fired up the engine. It now runs better than ever. No more idle control issues and the voltage on the relay pin is 12.8v

Who would have thought it would have had that much affect on fuel pump relay and hence idle control relay?!

So if anyone wants an idle control relay, I have a spare for sale!

05-11-15, 08:22 AM	#5
audimanur Grown up member Join Date: Feb 2015 Location: Yeovil Posts: 41	It runs okish with pump relay bridged, but I don't like the safety, or lack of, driving like that. For the time being I have disconnected isv and raised idle speed up. It stalls a couple of times when cold but is fine after 1 min of running. Doesn't stop the fuel pump cutting in and out very quickly tho! But at least people don't think I'm trying to race them at every junction!! I have ordered a replacement ignition module and will see if I can hunt the location of it! Cheers for the heads up on its location. I will report back The pump relay must receive a duty cycle feed from ignition module, so that it can control the isv and also the Rev limit function. There is a duty cycle on the relay pin, but I have no idea if it's correct or not. And I'm not really sure how it controls the function. Would love a wiring diagram to cure my curiosity!! Lol Last edited by audimanur; 05-11-15 at 08:25 AM.

04-11-15, 12:09 AM	#2
msh 4 ring whore! Join Date: Jun 2008 Location: Rucava, Latvija Posts: 3,816	Fuel injection type this time doesn't matter - it's ignition control module which controls fuel pump relay, and it's the same hella ignition control module for both K-jetronic and KE-jetronic. If you're really sure there's nothing wrong with wiring and relay, then next step is ignition control unit...

04-11-15, 07:22 AM	#3
audimanur Grown up member Join Date: Feb 2015 Location: Yeovil Posts: 41	Well, that is why I wanted a wiring diagram to test correctly. It must be getting the wrong duty cycle/hall sender signal from the ign. Module. Also, where is the module? I have hunted everywhere for it!

05-11-15, 09:22 PM	#7
audimanur Grown up member Join Date: Feb 2015 Location: Yeovil Posts: 41	The fuel pump relay isn't a basic relay. It controls rev limiter/idle control. There is a microprocessor on the board inside. This is why it is hard to diagnose with the correct info for the car

09-12-15, 01:13 PM	#8
audimanur Grown up member Join Date: Feb 2015 Location: Yeovil Posts: 41	OK, so I learnt a bit more once I actually found the idle control relay....... It is located in drivers side kick well, behind a plastic protector alongside the ign. amplifier. After testing wiring, I couldn't find anything wrong with the wiring other than the feed from fuel pump relay going. I tried a replacement idle control relay (262) and it made no difference. I then went back to testing the fuel pump relay. The issue had become worse and it turns out the small pin on the fuel pump relay only had a constant 10.5-10.8 volts on it. This comes direct from the ignition coil and the electronics in the fuel pump relay monitor this to allow relay to stay energised. I tested the voltage on the negative side of the coil and it also had the low 10.8v. I took the wires off the coil and found the resistance was higher than expected. It just so happened I had a brand new genuine coil sat on my shelf destined for my UR, its 99% the same. Checked the resistance which was lower and within tolerance. So I fitted it and fired up the engine. It now runs better than ever. No more idle control issues and the voltage on the relay pin is 12.8v Who would have thought it would have had that much affect on fuel pump relay and hence idle control relay?! So if anyone wants an idle control relay, I have a spare for sale!