Over fuelling and running badly.

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John-Ellis

John-Ellis

New Member
Posts
74
Hi all

I have this posted in "its a v8 mate" but it might be better in here.

I have a 1998 disco 1 with a 3.9 v8 duel fuel.

I had an issue last week which i thought i cured, but i was wrong.

Running on lpg she runs fine no problems at all.

On petrol she is properly over fuelling there is a smell of petrol coming from the engine but mostly from the exhaust.

Today i took out all the spark plugs and cleaned them up but the plug from cylinder 1 was wet with petrol and the other 3 from that bank was dry but smelled of petrol.

So i put a spark tester on plug 1 and it was lighting up just fine.

So we made a start at removing the injector for cylinder 1 as don1 thinks it could be stuck open and flooding the spark plug.

There is also smoke coming from the exhaust manifold on the left bank.

Can you remove an injector without removing the fuel rail from the engine?

Has anyone got any thoughts.

Thanks

John
 
Here's an update

A bit of a head scratcher after today.

First thing we decided to do was to use a mechanics stethoscope to see if the suspected injector was firing or not, we poked the injector a few times with the probe and low and behold it is clicking away, not only that but there is no over fuelling and the smell of petrol from the front and the back has gone more or less. We also found HT lead no 5 resting on the exhaust manifold.

We tied the HT lead back with string so it wasn't touching anything in the engine bay.

So we took it out for a test drive, she didn't stall on petrol and to be honest she didn't idle too bad, you could not tell much difference from the tone of the engine when switching to lpg either just felt that little bit rough on petrol.

SO THE PLAN OF ACTION

I have a new set of ht leads which I will fit next weekend and see how she runs with those fitted and since I have got them anyway I might as well as fit the O2 sensors.

See how she goes from there.

Cheers

John
 
haigy said:
Lamba sensor
Click to expand...


Hi Haigy,

That's what I thought originally to be honest until I took out the spark plugs and found one wet with petrol.

I have a set though and even though it's an awful job connecting the plugs together they will be fitted 😉

Cheers

John
 
For what 1 costs would it not be worth changing it as that would cause same problems as your having with the air mix in the e haust would then over fuel and run bad
 
Change 1 ha no chance for the amount of effort it takes to change them they are both getting swapped, you are correct though they do give the symptoms I'm getting, then again so does a faulty mass airflow sensor, hopefully next week we will be up and running.

Cheers

John
 
Ok guys,

I was hoping to post a good news update but its not to be......

So ht leads have been changed and the o2 sensors have been changed, but it didn't make any difference.

So it was left a couple of weeks and I thought even though the MAF sensor has already been changed I did buy a cheap one 36.00 from eBay.

So I disconnected the MAF sensor and started the engine and it ran great..... Until it got warm then it started running lumpy but it was not over fuelling however I did notice a bit of black smoke when I got the wife to rev it up to 3000 rpm or so.

A bit later I started the engine and whilst it was running I plugged the MAF back in and it started over fuelling again and running like a bag of crap I mean I couldn't even get off the driveway, so engine still running I disconnected the MAF and from then on it over fuelled and would not run properly.

The plan at the moment is to disconnect the battery for a couple of days to see if that clears any remembered settings in the ecu, then disconnect the MAF and see what happens when I start the engine.

Can anyone tell me at what point does the MAF sensor start giving signals to the ecu is it when the engine is warm or does it start giving signals from cold. I want to try and prove if it is the MAF thats duff or not.

I had a check for split vac pipes and I couldn't find anything.

Has anyone got any other idea's.

Cheers

John
 
discool said:
As soon as the air flow entering the unit it sends signals to the ECM. The fuel pressure regulator still has a vacuum pipe intact and connected ?
Click to expand...


Hi Discool,

Hope your all ready for Christmas pal.

I will double check that vac pipe on the weekend.

That's kind of good news about the MAF sensor I think.

Can I ask you run to through this with me, as to be honest I'm scratching my head as to what is going on.

So the engine from cold with the MAF disconnected ran great until it started getting warm, why would it start running rough, by that I mean some hesitation on acceleration but under load runs ok ish.

I can't get my head round why it runs lumpy with no MAF sensor when the engine starts to get warm.

I appreciate this pal.

John
 
Hi John, yes another Christmas I've seen a few so just them pass now, a bit like the whole of year it seems, where has that gone?.

Fortunately I've never had any issues with the EFI, but I've never understood that bit about the engine running ok without the MAF fitted, but any changes to the running of the engine when warming up or hot is down to the coolant temperature sensor, I suspect what u are seeing is a mis match of information going to the ECM hence the lumpy running.

I don't know if u have a copy of Rave I sure u have but if not it has the description of all the EFI components and their function.

Pete.
 
discool said:
Hi John, yes another Christmas I've seen a few so just them pass now, a bit like the whole of year it seems, where has that gone?.

Fortunately I've never had any issues with the EFI, but I've never understood that bit about the engine running ok without the MAF fitted, but any changes to the running of the engine when warming up or hot is down to the coolant temperature sensor, I suspect what u are seeing is a mis match of information going to the ECM hence the lumpy running.

I don't know if u have a copy of Rave I sure u have but if not it has the description of all the EFI components and their function.

Pete.
Click to expand...


Thanks Pete, I am sure there will be a way of testing the coolant temp sensor, I will whip it out over the weekend. I do have a coy of rave, I will do some more research.

Thanks again mate.

John
 
A couple of bits to bear in mind. The 14CUX ecu won't look at lamda when the engine is cold, the ecu needs to see something like 70 degrees before it applies lamda correction. The ecu also ignores lamda above about 3500 rpm. The basic setting of the air flow meter of a cat equipped engine is a CO trim at about 1.8v a non-cat V8 has a lower CO trim so in theory the cat car will be a bit richer when cold.

Unplugging the air flow meter when the engine is running should cause a fault condition in the ecu, it will then default to a limp home map which is typically very rich. You should avoid unplugging sensors when the engine is running but to reset a 14 cux either disconnect battery or unplug the ecu, you don't need to wait to clear faults, a few seconds should be enough.

With the exception of the switching on the lamda sensors all the other efi components can be checked with a multimeter.

One other thing, V8's sometimes run a bit lumpy at this time of year until they get a bit of heat in them, often it is a small amount of condensation in the distributor cap, once things start to warm up the condensation disappears and normal service is resumed.

Whilst what you have said so far might suggest an iffy air flow meter consider the ecu itself, it may be faulty. The other thing to maybe have a look at is the condition of the wires where they enter the plug for the air flow meter - there could be a loose or broken wire/connection.

Hope some of that helps.
 
Hi All,

So far looking round I cant find the correct coolant temp sensor for my 98 engine, I'm going to look into testing the one that is on the car with a multi meter.

Cheers for the advise so far it going to be a busy weekend.

John
 
Hi Pete,

I did look at that one, to be certain I will compare them on the weekend.

Can't wait for the weekend to come now, got loads to do lol

Cheers mate

John
 
Yes, that sounds about freeking right, well I can't bitch too much it is winter after all, bloody typical when you haven't got a garage to work in lol. Really hope it isn't going to be too bad I will be happy if I can just test the two sensors.

Really got my figures crossed that these tests show a defective part one way or the other, I can at least move forward with things.

Figures crossed my friend, figures crossed.
 
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