V8 update

In the cold weather it wouldn't start. Put a new fuel pump on it today, as the one on it was making irritable high-picthed whining noises and I was suspicious of it.

It now starts (after re-connecting the starter trigger wire to the solenoid) but it's still sounding lumpy at low revs and not firing up as easily as it should when hot. It seems to take too long for all cylinders to fire, some fire almost immediatetly and the rest chime in eventually. This is what it was doing the other day before fitting the new pump, except that it declined to start at all. Had all the plugs out then and some were wet with petrol while others looked sooty, as if they were the ones that were firing.

Ignition looks OK and sparks look OK, plugs are new and the leads on it came off the now-sold one where they never gave a hint of trouble. Dizzy cap looks new-ish, too.

I'm now wondering if it has one or more sticky/dirty/buggered injectors. This is a motor which has been standing unused for the best part of a year, which is why I suspected the fuel pump, having seen them fail in the past in such circumstances. Tomorrow, I'll try turning it over immediately I turn it on, rather than waiting for it to prime. It's booked to put it on the analyser tomorrow morning, which may shed some light.

Any point in bunging injector cleaner in it? or should I just replace them anyway, or try to clean/test them?

Reply to
Austin Shackles
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Injector cleaner is a LOT cheaper than injectors! You say it runs but lumpy, try squirting some cleaner at base of injector while its running, if it changes at all suspect injector seal on that cylinder.

Reply to
GbH

Austin,

I only suggest this because I don't know how big a job it would be but what is the feasibility of swapping the injectors around to see if the problem moves to different cyclinders?

Also could it be faulty coil packs? I'm not savy on the copnfiguration on more modern v8s.

My Dad was entertained by a duff new dizzy cap a few years back. It is possible it may be tracking. Do you have another Dizzy cap you can try. Also consider a new rota arm and check the carbon bush in the centre of the dizzy to.

I guess you may have already tried alot of the aboe but thought it worth throwing in to the melting pot just in case.

If of course the diagnosis kit would show the fault then let that happen first, time is quite literally money and its too cold to faff about outdoors looking.

Lee

Reply to
Lee_D

Just in case, it might be worth finding a local indipendant auto electrician, who understands the ignition and controls, also having the diagnosis kit, scopes and pickups.

Read this to find out why...

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OK, it's not a rangie, but if your ECU uses the same control method for coil pack current control (I have no idea if it does) could be nasty.

Either way, an experienced diagnostic guy could be cheaper to use in the long run.

Cheers.

Dave B.

Reply to
Dave Baxter

At the risk of invoking rule#35 which involves Grandmothers & Eggs ...

Tracking is easier to spot in the dark.

indeed

Reply to
William Tasso

On or around Wed, 20 Jan 2010 19:22:06 -0000, Dave Baxter enlightened us thusly:

fortunately, it's not a coil-pack one, it's still got a dizzy and just the one coil, I understand those :-)

It's hotwire-with-2-lambda probes, I need to read up on it a bit more...

Reply to
Austin Shackles

On or around Wed, 20 Jan 2010 12:39:33 +0000, Austin Shackles enlightened us thusly:

more update:

It's defintiely starting and running better with the new fuel pump.

Had it on the analyser at the garage, and at 3K revs or whatever speed it gets tested at, the lambda is a bit low and the CO is high.

At idle both are more or less OK.

Still sounds rough and missy on cold starting, which I suspect rather rules out a dodgy O2 sensor, seeing as they don't do anything initially, until they warm up, AFAIK.

So still thinking about injectors, and I've bunged a bottle of cleaner in it on the grounds that if it don't work, at least it only costs 6 quid.

Things I need to find out (anyone know the answer?)

1) It has 2 sensors. What happens if one is dodgy? 2) does it bank-fire the injectors like the earlier ones, or is it sequential?

It's running quite smooth and idling reasonably well and with about the right amount of power once warmed up. There's just a suggestion of roughness or occasional misfire when hot, at certain revs/load conditions - on hot starting it runs at about 1200 revs for the first couple of seconds and seems a tad rough, then slows to quite a smooth idle.

Reply to
Austin Shackles

Austin, does the dizzy have a condenser in it? If so try replacing it, they don't cost much. Had a strange misfire years ago and that eventually turned out to be the cause.

Reply to
Bob Hobden

And the Aldi £25 ultrasonic bath + some parafin/atf mix is ALOT more effective than 'injector cleaner'.

Gives you oppertunity to replace the base o-rings also

tim. .

Reply to
Tim..

If you've not already done it (you just said it "looked new"), I'd pull the dizzy cap off too and have a look, on one of my cars it still started and idled fine but was sometimes lumpy under load and at some points in the rev range despite the cap and rotor looking new on the outside while the inside looked like this;

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I'm amazed it ran at all, no central contacts either on the cap or rotor!

Reply to
Ian Rawlings

On or around Wed, 20 Jan 2010 12:39:33 +0000, Austin Shackles enlightened us thusly:

Injector cleaner in about 20 quidsworth of petrol (with some already in the tank) seems to have improved it, so I've bunged another bottle in today :-)

After that will see how it goes. It's starting way better, and pulling properly and more smoothly as well, so I reckon I'm on the right track. Might still end up replacing or refurbishing the injectors, will see if it goes through the test, in due course, assuming it's still running OK.

Reply to
Austin Shackles

On or around Sat, 23 Jan 2010 18:51:57 +0000, Ian Rawlings enlightened us thusly:

nah it looks good inside as well :-)

good point though. I once spent bloody ages chasing an ignition fault which in the end proved to ne a rotor arm which, although it looked fine, was earthing through to the shaft.

Reply to
Austin Shackles

In message , Austin Shackles writes

BTDTGTTS on Geoff's Minor MM; we had exactly the same fault. No spare rotor arm in shedspace, so we stuck on a complete distributor from a

1000, and all was well (in fact, it drove even better when we connected up the vacuum advance/retard, which the MM never had as standard).
Reply to
Andrew Marshall

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