Disco 1 V8 Just about starts, eventually...

Spent all weekend on this and I just can't work out what the problem is...

About 6 weeks ago I picked up a '97 Disco V8, drove it about for a few weeks then decided to tackle some of the minor problems, drove to the shops Friday evening with no problems, went to go out Saturday morning and it was really really reluctant to start. It cranks for about 90 seconds and with a bit of throttle tickling will just about wander into life after that runs ok idle is a bit rough but it pulls well.

New plugs, leads, dissy cap, rotor arm & fuel filter installed, no change. Checked and tested throttle position sensor, coolant temp sensor, fuel temp sensor, MAF & air gap. Spark appears good and strong, 11.5 volts at the coil on cranking & fuel pump is running whilst cranking. Looked all over for vacuum leaks but can't find any.... The 2 things I haven't tested fuel pressure (i need a gauge) and idle valve, i don't know how to test it....

Has anyone any idea what to look at next, or anyone near by have any spares I can swap around??

Thanks

Dave

make sure ignition amplifier switching correctly
across coil with a volt meter and crank- if the module goes bad it can affect ecu earth switching and no fuel

Sorry I don't quite understand, if I put a volt meter across the coil what am I looking for?

thanks

Cranking for 90 seconds is bound to have flooded the plugs, also you don't touch the throttle when starting , just key in the switch and turn.

Normally that's exactly what I would do but if I don't jiggle the throttle it won't even try to fire... Even when it does try to fire it takes ages to catch...

OrangeBobTail said:

Sorry I don't quite understand, if I put a volt meter across the coil what am I looking for?

thanks

Click to expand...

12 volt switching, if it isn't switching earth properly then ecu will not see pulses.

ignition on you should see 12 volt as not a ballasted coil as far as i'm aware, crank and you should get switching.

I had a disco I went out to with dodgy ignition amp, 12 volt to body earth and 7 volts with ignition on across coil- turned out faulty ignition amp and corroded pins

Ah, sorry I see what you mean now... Yes it is switching ok, you can see it with DMM across the coil & the plugs look to have a good spark. ECU is seeing the pulse as it runs the fuel pump whilst cranking (checked with DMM).

Just ordered a new coil & ignition amp, I don't think it will help but running out of options now....

OrangeBobTail said:

New plugs, leads, dissy cap, rotor arm & fuel filter installed, no change. Checked and tested throttle position sensor, coolant temp sensor, fuel temp sensor, MAF & air gap. Spark appears good and strong, 11.5 volts at the coil on cranking & fuel pump is running whilst cranking. Looked all over for vacuum leaks but can't find any.... The 2 things I haven't tested fuel pressure (i need a gauge) and idle valve, i don't know how to test it....

Has anyone any idea what to look at next, or anyone near by have any spares I can swap around??

Thanks

Dave

Click to expand...

Did you check your ignition timing? Also, check vac advance unit if that has gone that could well be your vacuum leak.

Testing idle control valve (stepper) is really just a question of taking it out and then tuning the ignition on and seeing if it moves. If you are going to do that you might as well just clean it up anyway.

You might want to think about taking off the plenum and giving it a good clean up inside together with the engine breathers. HTH

Thanks for all your help guys. Eventually found the cause of it, aftermarket rotor arm had failed with just 128 miles on it!! I bit the bullet and purchased a genuine dissy cap & rotor arm, all runs perfectly again :-D

The moral of the story is; don't assume a part is in perfect condition because its almost brand new...!!

Thanks

Dave

OrangeBobTail said:

Thanks for all your help guys. Eventually found the cause of it, aftermarket rotor arm had failed with just 128 miles on it!! I bit the bullet and purchased a genuine dissy cap & rotor arm, all runs perfectly again :-D

The moral of the story is; don't assume a part is in perfect condition because its almost brand new...!!

Thanks

Dave

Click to expand...

The moral of the story is don't use pattern ignition parts!!

Glad you got it sorted. 128 miles out of a rotor arm is not the worst, my RRC chewed one up in less than 5 minutes.

As Kev above which has been repeated many times.

I'm using genuine parts, fitted by the factory 15 years ago but I do have spares on the shelf just in case..