Cold start issue

MassiveJim

MassiveJim

MassiveJim

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22 Feb 2014
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Any ideas what this could be ?

I have a Mondeo ST220 on 148k
A "normal" startup on this car has no delay and engine starts as soon as the key is turned.
The problem I am having means I have to turn the engine over for 20 - 30 seconds then it sort of splutters and starts and runs fine.
This ONLY happens on a cold start and it doesn't happen every time.
I had it booked in to a garage to look at, following the phonecall I made booking it in, it got worse and was doing it every single time for a whole week, then it stopped doing it for a week, so I cancelled my garage appointment, yesterday it did it both in the morning before I set off to work and then in the afternoon when I was leaving work to drive home.

This morning it started fine again.

The car was converted to run on LPG about 90,000 miles ago, the LPG system was inspected and a fault found with a leaking "diaphragm" but that was replaced and the issue was still there.

When I turn the key I can hear the fuel pump priming itself, I have also tried letting the pump prime 3 times by turning ignition on/off before starting the car and it still did it.

has had plugs/leads recently. (in last 12 months)
 
And it only does it in a cold start? Does it always start up perfectly when it's warm?

Has the fuel filter been changed? Or the fuel pump? It sounds like a fuel pressure issue from a weak fuel pump.
 
Only ever happens cold.
Once the car has started I can immedietley turn it off and it would then start straight up.

Battery was changed recently.
LPG guy thought that there was perhaps a slow gas leak, and that when I went to start the car the inlet was full of gas and the car wouldn't start straight away because the mixture would be too rich and needed cranking until some of the fuel was cleared, so he changed the diaphragm which was split and would have been leaking but the problem still exists.

When the problem is happening it does seem to get worse the longer the car is left so his theory is sound, however I only tested it once by starting the car after being parked up for 3 hours. Normally the car is parked for 8 hours+
 
It does sound very much like a fuel pressure problem. The fuel in the line drops when it's left for a while then it takes quite a few turns to get the pressure back. My money would be on a weak fuel pump and/or leak in the fuel system (maybe injectors).
 
The fuel pumps have been known to fail on these.

Annoyingly you either have to drop half the underside of the car including the exhaust to drop the fuel tank, or enlarge the hole under the rear seat in order to remove it.
 
Cycle the key a few times (without pushing through to 'start') and see if it then lights up the first time when you attempt to start it. Could point to a fuel pressure issue.
 
Gaygle said:
It does sound very much like a fuel pressure problem. The fuel in the line drops when it's left for a while then it takes quite a few turns to get the pressure back. My money would be on a weak fuel pump and/or leak in the fuel system (maybe injectors).
Click to expand...

Also on this, would I not expect other symptoms if the fuel pump was failing ?
ie poor performance or struggling at high revs etc ?

Performance is spot on once car is running, LPG gives slightly less overall BHP than Petrol and I can still feel the slight improvement in performance when the car is running on Petrol.
Which sort of indicates to me that the fuel pump is actually ok.
Im not well versed in fuel systems however so I could be completely misunderstanding how it works.

As for the leak, would a slight leak cause the smell of petrol ?
I haven't smelt any at any point.
 
So if the car runs and starts without a problem after the first time then, may be the fuel is being allowed to draw back into the fuel tank.

Is it direct injection?
 
MassiveJim said:
According to wiki it uses sfi.

What would prevent/allow fuel to draw back into the tank ?
Click to expand...

Looking on the web cold start like this is often todo with the injectors (in diesel) - wonder if the same with the injector for the LPG?

Just thinking that with air being allowed in (seal problem) that it will need to be primed before it will start (I mean the fuel re-drawn from the tank).
 
MassiveJim said:
As for the leak, would a slight leak cause the smell of petrol ?
I haven't smelt any at any point.
Click to expand...

You could have an internal leak.

Normally the fuel pumps incorporate a non-return valve. These can fail.

Also, you may have a leak in the fuel pressure regulator which might also allow the system to lose pressure when not running.

Neither will result in an external leak and petrol smells. but either or both might make the first start of that day take a little longer.

But there is something about the description of the fault that suggests to me that the fault might lie elsewhere. But to confirm one way or another you will need access to a fuel pressure gauge and carry out a fuel pressure test before looking at anything else really..
 
So a little update on this, and some more thoughts from your good selves.
The problem still isn't fixed.

I took the car to a garage an hour away so that he could look at this, the reason being I believe it to be a gas issue and my local garage doesn't deal with gas.
He had the car for 2 weeks and it started up first time every time.
There was another issue with the car reporting running lean, a smoke test revealed a leak on a vac pipe that has been replaced now and on the exhaust (which is being looked at next week)


Since I have had the car back (picked up friday) it has had this cold start issue every day.
It doesn't even need leaving that long either, I drove 12 miles to KFC and we sat in so around 45 minutes ? and it had the issue when we came out.


I can hear the fuel pump prime up every time I turn the key in the ignition with no change in tone, I have just been out and turned the ignition on and off about 10 times in the hope to fully prime the fuel lines to rule out the pump and the FPR, and it still had the issue.
I think this safely rules out the FPR and pump anyway.
I did for a while believe it could be a leaking injector, but if that were the case I think it would fire up but run lump for a few seconds.


It could be coolant temp sensor but I think if that were faulty then it would give more problems would it not ? ie rough running at other times etc.
There has been an ever so slight fuel/oil smell in the cabin for a couple of seconds a couple of times when this has happened.
 
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