Suspected Fuel Pump issue

[SamC]

Hi guys,

I have a 94 Disco.

It runs perfectly except that occasionally (can't figure out circumstances that causes it - may be due to the car being parked on a slope) it will stall or fail to start after being parked. It cranks and revs and then dies almost immediately. It does this for about 5 minutes continually turning the ignition and then eventually it revs really high and stays on and works perfectly once again.

I hadn't driven it for a while (2 months) until yesterday and then tried and it did the same as above but took a lot longer to start. I looked up a few forums and a few suggested turning the ignition to the second point and leaving it there for 5 minutes. I did that and it restarted first time and ran perfectly.

I can hear the fuel pump whirring for a few seconds when I turn the ignition. I have recently replaced all the spark plugs.

My question is (and I am very new to the whole mechanical tinkering business so please bear with me) how can I test the fuel pressure to see whether I am dealing with a fuel pump issue? Is there anything else that would be relatively easy for me to check and test and if necessary replace?

Thanks for any help you can give me guys, I really appreciate it.

Edit: just a little bit more information. When I started the disco up this afternoon I heard a fluid swishing sound under the centre console or dash that lasted for maybe 2 seconds. Not sure if that is related or any help in tracking down the problem. Thanks again for any help guys.

[Gary S11]

Hi I think they have a anti drain back valve in the pump....it's not a real hard job to fit a v6 Holden replacement / Bosch pump..but bee- utey ( member) will come on here and he will definitely will be able to help you...Gary

[sheerluck]

There's a Schraeder valve on the fuel rail on the post-95 V8s, not so sure about the early ones. Bee utey is definitely top notch with these.

[SamC]

Thanks. There was a post a while back with the title 'air in the fuel line' that I posted on earlier today. The symptoms with that one seem pretty similar to mine. Not sure what the outcome with that was, but it has lead me to think that maybe it isn't the fuel pump.

[bee utey]

Thanks. There was a post a while back with the title 'air in the fuel line' that I posted on earlier today. The symptoms with that one seem pretty similar to mine. Not sure what the outcome with that was, but it has lead me to think that maybe it isn't the fuel pump.

The other thread is about a diesel which doesn't run an in-tank pump. The diesel runs a lift pump attached to the engine.


Your pump pressure can be measured at the fuel rail so long as there's a schrader (tyre type) valve on the fuel rail. You will need a screw-on pressure gauge otherwise fuel may spray everywhere. The important thing with EFI fuel pumps as Gary S11 posted is the check valve in the pump that holds line pressure after it is turned off. So if the pressure holds after turning the engine off the pump isn't the problem.

Now as to your actual problem, have you tried using the accelerator on start-up? It may be just the idle speed controller (stepper) sticking closed.

Another possibility is your ignition switch is faulty, if the engine stops running as soon as you release the key.

[SamC]

Thanks for replying bee Utey.

In relation to the ignition and accelerator - I would only need to turn the ignition once and then if I kept pressing the accelerator up and down in would keep it revving but never really firing if that makes sense. The revs would go from near zero to 1000 and back as long as i kept pressing the accelerator up and down (I couldn't just hold it down). As soon as I stopped it would die.

When i was last driving it around, before I started her up yesterday, it stalled 4 times whilst driving. Twice after taking off at lights, once just driving along and once driving down a hill and turning off. The car just lost power in all instances. It was hard to start perhaps 5 times. Each time I would keep trying to start it and it would rev up and then die straight away (regardless of whether I kept the key turned or not).

The most consistent thing was every time it restarted (normally after about 5 - 7 minutes) it would rev high and then settle and drive perfectly. At all other times it idles fine and is powerful when it drives.

Thanks again for your help bee Utey, any help you can give is greatly appreciated.

[bee utey]

Well it sounds like you're getting enrichment every time you press the accelerator (just like a carby has an accelerator pump) and it's running just on that. I'm not really an EFI expert but that sort of thing could come from low fuel pressure, a dodgy throttle position sender (TPS) or air flow meter (MAF). You need someone to plug it in to a tester of some sort.

[Stumpy1]

Hi Sam C,

Agree with Bee utey except for the Dodgy Throttle position Sensor (TPS). I have just replaced my TPS after diagnosing it's failure. The v8 will start and idle easily even when the TPS fails.

Hope this helps eliminate one suspect.. Good luck

[SamC]

Excellent, thanks again. That gives me something to look at.

If it is a fuel pressure issue are there many separate parts that could be leading to the problem? My first thought is fuel pump, fuel filter, fuel injectors, fuel pressure regulator, and all the others I don't know of... Are some more likely to be the problem than others?

If it is the Maf, is it just the single part (the Maf sensor) that needs to be replaced to ascertain whether it is problem or not?

I'll take it in somewhere and post back what the problem was, just nice to have an idea when I'm talking to them about what the problem might be so I don't end up walking out with a whole lot of parts that I don't need.

Cheers

[OlliesLRover]

Might pay to put the Coolant Temp Sensor on your list of possible culprits as it can show the same symptoms as you are having.

Approx $30 new

[Stumpy1]

Might pay to put the Coolant Temp Sensor on your list of possible culprits as it can show the same symptoms as you are having.

Approx $30 new


Yeah good call on this one OlliesLR and easily overlooked too. Sounds silly but I believe the fuel mapping relies on info from coolant temp sensor for part of its mixture calcs. At $30 its not going to break the bank to try.

Did you try Bee uteys suggestions with the fuel pressure??? This would be an excellent place to start you investigation. When it misbehaves, has it done it from both cold starting and hot starting??

[SamC]

Just checked and the fuel rail has the valve bee utey was talking about. I'm just about to head down to SuperCheap to pick up a fuel pressure gauge and then I'll check it. I'll let you know what it shows.

Thanks again everyone, greatly appreciated.

[jonse]

A failing fuel pump will give the symptoms you describe, combined with a sticking idle control valve. The high idle revs being due to the Idle controller trying to increase the idle speed when it is very low (due to a lack of fuel pressure) and then being unable to bring the idle speed back down quickly enough when full fuel pressure is provided.

I had similar symptoms when my fuel pump was dying.

[SamC]

Seems a fuel pressure gauge is hard to find. Supercheap don't sell them and two Autobarns and a Burstons were out of stock. Will call around a few places to find one.

I forgot to answer whether it happens cold start or hot start. I can't remember it ever happening first thing - eg after it has sat all night. Every time was when I had driven it for 20km or so and parked for 2 hours and then tried to start it again; and the few occasions it stopped in traffic.

Aside from the restart on those occasions, the idle seems to be perfect and it always has great power.

When i test the fuel pressure, is it possible that at the time i test it the fuel pump is working well but that it may cut out at different times (those occasions it has stalled or failed to start)? Just seems strange that it will drive really well for so long and then without warning stall and once it gets up and going again it drives fine again.

[SamC]

Sorry for not updating this for a little while. Was away for a few weeks.

Haven't yet bought a fuel pressure gauge (don't really want to spend $100 plus on one when I will likely only use it once) but have looked at a couple off eBay that I might get.

Anyway, tried to start the disco up after our holiday and had the same problem as I have outlined earlier in the thread. After quite a few goes (30 attempts to start over an hour or so having to pump the accelarator to keep it idling) it would idle rough by itself but never really kick in if that makes sense (always sounded like it was about to die and wouldnt respond to the accelsrator). I opened up the air filter box and just blew through it and cleaned a few bugs out and had a look at the maf (didn't do anything to it, basically just looked at it) and put it all back. Perhaps a coincidence but after i put all that back it then started first time and idled perfectly and has continued to run perfectly since then.

Sorry, I know the fuel pressure gauge is important to diagnose this problem, I'll get one, just need to find one that is an ok price. Also, I may be open to the possibility of buying a code reader. I know very little about that, so if someone could enlighten me as to whether I can get one for the disco (1994) that would be great.

Cheers again for all the help.

[streaky]

One of the best.... and thank god the cheapest of the 14CUX code readers is the ECUMATE..http://www.ecumate.com/. I think I paid 150 UK Pounds but check the site. They also have the fault code display but for the extra money get the actual ECU Mate diagnostic reader...it's worth it.

I made a very cheap and efficient fuel pressure gauge from a glycerine filled gauge available from some of more technical accessory shops here.
I then took it to a place who make hydraulic hoes and they fitted the appropriate hose and fittings.
With the 1 1/2 meters of pipe draped over the bonnet I can watch the pressure as I'm driving.