DIFFICULTY STARTING WITH ROUGH IDLING AND CUT OUT

1997 Isuzu Trooper

Tiny

wulliewill

September, 18, 2011 AT 8:17 PM

HI, it's a 3.1tdi manual I have. This is an issue that has just started with no prior indications of any impending problem; It cranks over and won't start, but on the 3rd attempt, she fires up. The idle speed then goes up and down. When it dips, it sounds like it's going to stop, but then catches itself and continues to run, but then most times it cuts out when the revs dip. I pottered about with the fuel filter and retightened all the hose claps etc. With this, I managed to get her moving again, but when changing up to 2nd, the engine seems like it's being strangled of air or fuel? Then it cuts out and it's difficult to restart. Where is the best and cheapest place to begin the problem solving? Does this model have a fuel pump or sender in the fuel tank that could be causing this? Could it be a hole in the fuel line, if so would it be the feed or the return hose that might have the perforation? Could it be an external fuel pump issue? Does this model have an EGR valve than could be the issue? Or could it be an injector problem (God forbid!)?
Not sure where to begin the search with the best logical approach, your help would be most gratefully appreciated.

Cheers

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Tiny

DrCranknWrench

September, 18, 2011 AT 9:50 PM

The best place to start is to check the fuel pressure. Then start diagnosing whether it is fuel management or igniton that is the problem.
If the pressure is low, either there is a bad connection, the pump is failing or there is a clog ina fuel line.

Check for spark by either grounding a plug on the block and turning over or test the coil for 12 volts.

Here is a walk through on diagnosing and understanding fuel sytems.
Follow the link below by pasting it into your browser.

http://www.2carpros.com/articles/engine-stalls

I hope this information helps.

Tiny

wulliewill

September, 21, 2011 AT 2:48 PM

Hi thanks for the reply. Having been working with the fuel filter, I can add a touch more description. When the engine cuts out, I can hear fuel running back into the fuel tank, which perhaps suggests that there is a hole or break in the piping to the fuel pump. I think the fuel pump is working and it still draws fuel through the filter, but must be drawing in air perhaps one the demand for fuel increases? I blew the fuel lines clear so we can look past a clogged line. I read through the info in the link you provided. I am still a bit bewilderded, I could attribute any of the diagnosis' to what may be happening, simply due to ignorance, and as when I seek to inspect things, I am not sure what they are as I am not familiar with the ancilleries on this engine, they don't look like ones I have exprienced before. It would help if I knew what the various parts were called and where to find them (Looking for something like a Haymes manual) Where is the best place to check the fuel pressure and how would I judge it's performance? I would need to advise that it is the 3.1 diesel engine it has and not a petrol version. Pity it wasn't petrol, I would have a better mind of what might be wrong; this is the first diesel I have had to problem solve.

Many thanks,
Wullie.

Tiny

DrCranknWrench

September, 22, 2011 AT 1:20 AM

What you are hearing is the reurn fuel ine. If you can hear it draining back, fuel pressure may be an issue as this is the high pressure line.
Unfortunately being in the USA, I don't have the test pressure for the diesel.
The petrol pressure, and probably the diesel can be taken of the fuel rail with a fuel pressure test gauge. If you can't find that test port, I have a diagram that shows a test port connectore between the fuel filter and fuel rail. The test gauge should have an adapter to fit the threads of the test port.
The spec for the petrol motor is 3.0-3.9 kg/cm 2. I don't think the pressure is the same for a diesel, but you can probably double check it on-line or get it from a parts store. I actually have some European specs and as this was the pressure spec for all, it most likely is the same for diesel, but I cannot say that with 100% verification.
Test it and if it is not up to spec, the may be an obstruction in the line causing pressure loss. I think doing the in-line fuel filter is definately the best move for now as if it is the original, it is surely impeding the fuel flow.
Get back to me with the results.

Tiny

alanbeech

January, 3, 2013 AT 7:40 PM

Having had 5 of these vehicles in 3 countries I can tell you withought doupt problem is rotten fuel pipes on top of fuel tank ! Easiest way to acess is cut hole in floor over tank. I am now doing this for the third time. Alan

Tiny

DrCranknWrench

January, 4, 2013 AT 9:15 AM

That is a really horrible thing when manufacturers use cheap metal. Especially in an area where safety is an issue.

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