2.5Crd Rear Fuel Lift Pump Won't Stop Running - Help
Posted 07 February 2017 - 06:33 PM
Posted 07 February 2017 - 06:50 PM
I swapped the relay and everything was fine.
It started happening a few weeks later and found out that the negative connector to the battery had become corroded, got a new g clamp for the cable and it fixed it!
I was only doing it because the engine would cut out after going over a speed bump, didn't mean to fix the fuel pump lift.
Maybe it was a red herring but it's worked *touches wood*.
Maybe have a look at your battery connections?
Posted 14 February 2017 - 06:10 PM
Can someone remind me what is supposed to happen - it's been a while. You turn the key (2001 mk4), the lift pump whirls for 10 seconds or so, then it stops. Am I correct? Mine keeps whirling indefinitely.
Posted 14 February 2017 - 06:42 PM
Yes you're correct (Mines 2005 2.8CRD with rear lift pump and filter in the pump housing), turn ignition key on and you'll hear the pump run for approx 7-10 seconds (Just checked mine, 7 seconds) and it cuts out.
I'm not sure if this is controlled by pressure switch or just a simple timer, that would be interesting to determine as I wonder if you've got a leak, the fact you get engine cutting out makes me think more you've got a leak or a hole/damage somewhere that when pump is running it's pumping out and when under heavy load it draws air in and chokes the engine.
I know you've checked the fuel lines, etc, but I'd go again along those lines, switch on and let the pump run and then follow the pipes and look for any seeping fuel, etc.
Also, if you run the fuel pump for a while (30 seconds) does it's pitch change or differ at all? I'm wondering if as it builds pressure up and up that the pump would then start to struggle to pump due to the pressure increasing?
Sorry no answers just more questions and things to look for I'm afraid.
Posted 14 February 2017 - 07:45 PM
Any ideas as to how it determines the pressure? I could scrap the car, but this is now more of a matter of the ultimate challenge that I can't let myself fail!!
Posted 15 February 2017 - 09:21 AM
Also thank you for replying on my other thread, that's the importance of these forums they all help us out in times of need!
Right, yes that's a good point, I forgot when I replaced the filter that it seemed to run longer to prime the system (Can't 100% confirm that as I didn't really pay attention to it!) so that does suggest a pressure sensor and that could well be what we're looking at here as if that was faulty then it could cause the issues.
Looking at the exploded diagram of the pump there isn't any sensor/pressure control in there http://i.imgur.com/bM4Jk.pngWhich makes sense, the sensor would be in the engine bay at the end of the pipe run (i.e. where the pressure needs to be).
Oh also take a look at Daz's video on a pressure relief valve failure on the pressure rail, this might be a simple test to try.
I've not got the workshop manual installed at the min so will do that and try to find the fuel pressure sensors, as if we can track them down then focus where to look for the potential issue.
Posted 16 February 2017 - 10:06 AM
Have dug out the workshop manual, and looking at it there is only one "fuel rail pressure sensor" but that's on the high pressure side:
The diagnostic part of it goes on to explain:
DIAGNOSIS AND TESTING - AIR IN FUELSYSTEMAir will enter the fuel system whenever fuel supplylines, separator filters, injection pump, high-pressurelines or injectors are removed or disconnected. Airtrapped in the fuel system can result in hard start-ing, a rough running engine, engine misfire, lowpower, excessive smoke and fuel knock.Inspect the fuel system from the fuel tank to theinjectors for loose connections (Refer to 14 - FUELSYSTEM - WARNING). Leaking fuel is an indicatorof loose connections or defective seals. Air can alsoenter the fuel system between the fuel tank and theinjectors because the lift pump only runs to primethe system. It does not run while the engine is run-ning.
Which helps us here, so the lift pump should only run to prime the system and not whilst the engine is running.
And now the bit you probably don't want to hear, the IPM controls how long the lift pump runs for according to this:
So I'm not sure where that leaves us, if it's constantly running then there are two things to check, either the IPM is constantly sending the 'energise' to the relay (not good news) or the relay is sticking in the 'energise' position. You can test this by removing the relay, finding the correct terminals (You're after the supply two terminals) and using a multimeter set to DC voltage and turn ignition on, you'll get 12v (ish) for up to 10 seconds then it should stop. If you get that, then the IPM is doing it's job and it's the relay.
Even though a relay looks ok and sounds ok it can still be corroded and cause arking, false failure, jamming open/closed, etc, so I think that's the place to be looking.
I'm unsure what that pump running constantly would cause with the rest of the fuel system though so not sure what it would cause.
Posted 18 February 2017 - 09:02 AM
Posted 11 March 2017 - 12:07 PM
Hi, I as well keep trying to start the car for over a year, today it finally started.
Related to the fuel lift pump, I disconnected the fuel supply to the high pressure pump it is one of the two near the maf sensor), in a fuel can I put a long translucent hose( so it seats on the floor and the fuel can be seen) and I turned the ignition on and off several times( about 30 times), I removed about 10-15 litres, until no bubbles were visible on the hose. Make sure is enough fuel in the tank ( I was putting it back in the tank as the can was filled up) and also make sure the hose it seats dipped in the fuel( live about a litre in the can).
The lift pump I guess is controlled by a timed relay, """only guessing"" if the original relay was faulty and you fitted a different one, it may not have the same components in it, try to get a same one if that's the case.
Mine had more problems than that, which were discussed in other threads, thanks to Andyb200 ( also thanks to others that replied to my posts) I had very good points where to start from.
Hope it helps.
Posted 22 March 2017 - 10:27 PM
Posted 22 March 2017 - 10:28 PM
Lift pumps on diesel.
Posted 22 March 2017 - 10:28 PM
Posted 22 March 2017 - 10:31 PM
Posted 24 March 2017 - 10:14 AM
2.5 and 2.8 are practically the same engine. Above the filter is a pump that primes the fuel system when the ignition is on....the high pressure pump doesn't even start until the engine is cranked. If the fuel supply to the high pressure pump is removed and ignition is turned to on position, fuel will come out. I've done it, to remove air from the system I removed about 15 litres of fuel pumped by the lift pump.
On your several 2.8 engines. when the ignition was switch to on position, could you hear a buzz coming from the rear of the car?That is the lift pump or the prime pump, unless you have/had a different engine or fuel system fitted but I doubt it.
Posted 24 March 2017 - 02:20 PM
Having owned several 2.8 crd models can I categorically state that they do not have lift pumps and rely on the high pressure pump to suck fuel from the tank. There is a manual primer on the filter housing.
HiYs, some EuroVan 2.8's are HP mechanical, filter in engine compartment. Others even of the same year are ' Lucas style' electric lift pump and filter near the rear fuel tank.
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