Fuel Pump and Fuel Relay fine, Not priming on start up.

Hello everyone,

I’m hoping the joined wisdom of the forum can help me with a confusing issue with my girlfriends new Hijet. This is my first post here so go easy on me, I’ve been working with this van less than a week and will probably need idiot proof explanations.

We bought the van knowing that it would need the fuel pump replaced, it was covered in bodged wiring under the dash and almost every circuit has seen a bad crimp job or 2. I fitted (and bench tested) a new fuel pump and wired the connections there to hook back into the original loom. Someone had put a ground straight from the battery to the pump and tried to fit some sort of cutoff switch in the cabin. The wiring was frankly unsafe and it no longer worked so I set about repairing each connection properly and chasing each wire back to its destination checking continuity as I went.

The goal was to return the harness and everything on it to stock and correct operation, I have been using the wiring diagrams and loom wire lists from the manual to ensure everything is where it needs to be.

The relay block was missing the fuel pump relay so I ordered another, I couldn’t find any information for a Denso part number so ordered an identical one to the main relay, hoping this was the right part. It’s a Denso 056700-9160, is this correct?

So I know the pump works as when I jump the 2 fuel pump relay terminals (as outlined in the manual when performing an injector efficiency test) I hear the whir and the van starts straight up, the problem is that when I replace my jump wire with the relay, the pump does nothing when the key is turned. I have also checked both relays are functioning correctly and have checked their resistance so I can be sure it’s not either of them.

All fuses are ok and have been replaced. EFI fuses under glove box and the fuse box at the side of the wheel have both been checked.

I’m really confused as to what could be causing the lack of signal to the pump through the relay as I have checked the wiring too many times to count now and the terminals are all in the right places..

The low power side of the fuel pump relay has one wire which goes to the ECU (black and white) and one which links to the main relay and the travels to EFI Fuse 2 (blue/black) I’m getting absolutely no voltage through this when the key is turned and I’m guessing that’s whats stopping the relay from energising, I just can’t understand why.

Obviously I can actually run the van using the jump wire but then the fuel pump is going the whole time, there is no timed cut out after it finishes pressurising the system.

suggestions on potential causes are most welcome.

Thanks in advance.

Beaner

Welcome. Have you got power at EFI fuse 2 when the ignition is on? If not, the wiring is not fully fixed. This diagram (kindly supplied by HighlyJetted) may help.

I don’t have any power at EFI fuse 2! This is progress, and at this point I’m thankful for it so cheers. Currently investigating and will report back when I’ve got juice going to the right places. Fingers crossed

Ok I have power to EFI fuse 2, I think maybe I jumped the gun and didn’t test it right. But ignition switch goes on, and I get 12v at the fuse. My continuity between the wires pictures above all seems correct, so once again I’m out of ideas. Any suggestions?

Well, I'm not certain you have the correct relay, as the numbers on the drawing differ between the relays - though I'm not sure what difference that would make. If you have power going to the coil side of the relay but the coil is not energising, then the ECU is not completing the circuit. Whereabouts are you, and is the van a 1.0 or 1.3?

Yeah that’s what I figured, the ECU isn’t playing ball from it’s side. Is there anything that can be done about that or it replacement time?

I’ve checked everything else to the nth degree and it seems to just be a problem with that side of that relay so it must be that.

Do you by any chance know the correct relay part number for the fuel pump relay? I just guessed it was identical as I couldn’t find anything to the contrary But I could be wrong. I mean it’s doing the job when I manually ask it so I don’t think it matters too much, like you say.

The van is a 2000 1.3 EFI, and I’m located just outside Croydon.

Not sure, I'll try and have a look this afternoon if I get a chance.

Thanks very much for the help.

Sorry, it was pissing down this afternoon, but have you seen this post?

wrightgeordie wrote:I inadvertently blew the fuse for the fuel pump on my van the other day whilst refitting the petrol tank.  What I thought would be an easy fix via the fuses in the main fuse block turned out to be a bit more complex than I first thought.  The main fuses were all OK so I turned to the fuel pump relay looking for a solution, the relay block is behind the instrument binnacle and is easily accessed.  I had to check all four relays as I couldn't identify what the function of each was, fortunately they were also all in working order.  This prompted an extended search for an inline fuse and after a bit of a root about I found a twin 15 amp fuse block wrapped up in the wiring loom on the passenger side adjacent to the ECU.  Hey presto a blown fuse and after replacing it a working fuel pump.  I don't know what the other fuse in the pair is protecting but I think it's well worth knowing it's there if your having electrical problems.

I've just found out how to post pics - here it is

You can see the fuses the ECU and the space for the glove box

Yeah I did see that, that’s EFI fuse 1 and 2 I believe. I went through all the fuses when we got the van ( most weren’t even the right rating!) and have been periodically sanity checking them as I’ve gone along. I’ve also checked that I get power to the correct terminals when the ignition is on, which I do.

I’ve ordered another ECU off eBay for the grand sum of £27, at this point I’m quite convinced it’s the pin in the ECU not doing it’s thing so I’ll change that and see where we stand.
Many thanks for the help so far, hopefully it’ll be sorted soon and I can relax knowing I’ve not convinced her to spend £600 on a lemon!

Hi. I'm not fully conversant with the EFI system on the Hi-Jet as mine has a carburettor. However, I am a fully qualified car mechanic and I'm conversant with fuel injection systems generally. The way the system works, is that the main relay poweres up the ECU with the ignition on and this in turn powers up the fuel pump relay to prime the system for a few seconds. The ECU will then switch off the fuel pump unless it receives a pulse signal from the crankshaft sensor or rev counter. This signal tells the ECU that the engine is rotating so it can continue to supply a live feed to the fuel pump relay. This is a safety feature so that in the event of an accident, the engine will obviously stop rotating and the ECU will therefore switch off the fuel pump to save fuel being pumped out of a severed fuel line. Some fuel injection systems use an inertia switch to cut the fuel pump in the event of an accident so I'm not sure which of these safety features the Hi-Jet has. Getting back to your query, I would think that you have either got the wrong fuel pump relay ( missing the terminal for the engine speed pulse ), or you still have an wiring issue somewhere. I'm sorry I can't help further, good luck with your investigations.

Hi, thanks for the reply.

I bought a new ECU, plugged it in and the relays started working properly! New oil and plugs and It’s running really well now.

I have heard a lot of people say the denso ECU’s are quite bulletproof but it seems the original had a blown pin and wasn’t doing its job.

Wiring has been a constant battle with a previous owners handiwork but I think (fingers crossed) everything has been rectified. Even got new fog lights and a reverse light wired in, very fancy!

This also means that the main and fuel pump relays are interchangeable and the same model can be used for both (if this isn’t already the case.)

Thanks again for the insight.

You will probably find the burnt away pin is human intervention, caused by the last bodge artist who was trying to "fix" it before you got it. Many people make things worse with their efforts! This is something I see in the fault finding game more often than not.

Thing is, the bodge looked like more effort than fixing it properly.. I wish people wouldn’t touch a soldering iron without learning how to solder first! It would make so many jobs easier.