Combo C 2002/2004 - Combo C Fuel Pump fault after engine transplant

Honest John Back Room » Technical matters
What is life like with your car? Let us know and win £500 in John Lewis vouchers | No thanks
View Threaded
Wed 31 Dec 2014 00:43
Combo C 2002/2004 - Combo C Fuel Pump fault after engine transplant - ianz

Hi .. I have a Combo C 2002 petrol van which had a toasted engine. So I obtained a similar (originally I thought identical) engine from a 2004 Combo C van and swapped them over. Now there is no fuel pressure and in fact no power to the fuel pump. Both engines have a 6 way connector (only four ways are used) that inludes a blue/red wire that carries 12v to the fuel pump. But the two engines have a different style of connector, so are not directly interchangeable. However we have traced the wiring and determined that the blue/red wire passing through this connector actually carries 12v to the pump, and putting 12v onto this wire makes the fuel pump run. So far so good.

But when we connect the 4 connector wires, color to color, the fuel pump doesnt run. We have checked the fuse and is OK.

Can anybody watching explain what actually turns on the power to the fuel pump and how the pressure regulation system works. I presume that the ECU controls all of this, but am not sure.I am tempted to just hotwire 12v onto that blue/red wire..but am fearful that the pressure regulation might involve fedback via the ECU so could have a bad outcome.

Any information would be helpful. TIA.

Reply | Report as offensive | Link
Wed 31 Dec 2014 09:05
Combo C 2002/2004 - Combo C Fuel Pump fault after engine transplant - elekie&a/c doctor

The red/blue wire is the power supply to the fuel pump and the injectors.This is switched from a relay in the engine bay fuse box.There could be other differences on the engine wiring .Can you use the original engine wiring?Also have you used the original engine control unit and make sure the earth wire ring terminal is bolted to the ecu.The fuel pump and injectors will not switch unless the engine control unit reads an engine rpm signal from the crankshaft sensor.located at the rear of engine,by gearbox.

Reply | Report as offensive | Link
Thu 1 Jan 2015 05:18
Combo C 2002/2004 - Combo C Fuel Pump fault after engine transplant - ianz

Thanks for those suggestions elekie&a/cdoctor. So far I am using the original car wiring and the replacement motor wiring and ECU but may resort to replacing the motor wiring/ECU with the original set if I dont find a solution to this problem.

However the crankshaft sensor and associated wiring seems to worth investigating as a possible cause of the lack of the power to the fuel pump..as you suggested. In addition there are two more things pointing to the crankshaft sensor. Firstly I read the MIL flash code and one of the codes was 0335 which is a crankshaft sensor fault. Hmm..The other reason is that the van that the replacement engine came out of had a frontal impact damage and in fact the screened cable to the crankshaft sensor had been severed in the impact. I have repaired the break, but it all seems too suspicious imo.

So I took out the crankshaft sensor out and metered it at 2.3Kohm which compares exactly with the one from the old engine. I also connected it up to a scope and when I crank the engine I get a 200mV p-p sine wave off it. so that all seems good.

Now I need to know where this screened cable ends up so I can check the wiring. I presume it goes to the ECU..but then again it is dangerous to presume anything when you know as lillte as I do. Any further ideas or info apperciated. Ianz.

Reply | Report as offensive | Link
Thu 1 Jan 2015 09:56
Combo C 2002/2004 - Combo C Fuel Pump fault after engine transplant - elekie&a/c doctor

You must use the original engine control unit as it is coded to the electronic network/immobiliser system of the car. The screened wire is not too important as it is there for interference issues.I not sure where it runs to ,but probably connects to one of the ground points in the wiring loom.

Reply | Report as offensive | Link

10 warranty myths exposed

Here’s how to sort the fact from the fiction when it comes to car warranties.

Cheap Car Warranties

From which small car to buy at which price point to the best UK-built cars, our Top 10s have the lot. Click now for your shortlist.

Unsure of what to buy? Our Top 10s are here to help you....