Hi, anyone got an idea on the problem here?

I have a 1988 xr3i MFI, it starts first crank no problem, it will run for about 5 minutes then just dies and won't start again until cold, doesn't even kick slightly just cranks and cranks.

Fuel pump still primes.

So far I have changed...

Ht leads
Plugs
Rotor arm
Dizzy cap
Coil

Any ideas?

 

Fuel related for sure.

Warm Up Regulator(WUR) - it has a bi-metallic strip that heats up and changes the fuel pressure as it warms (in unison with the engine). In these temps at the mo, going from fully cold to warm-ish will prob take 5mins, so it tallies up.
They are easily stripped and cleaned up, but doing that is useless if you've got no way of validating the pressures. You can easily make a DIY fuel pressure tester for these, and you'll be able to see the pressure behaviour as it warms up. It works backwards to how you'd expect if you're measuring between WUR and metering unit - cold it will be around 1.3bar, warm you should expect around 3.6bar. A strip and clean doesn't always do the trick - but again rebuild kits are available - or just get a known good unit.

If the CO adjustment screw in the metering unit is well and truly out of whack, it might be able to run when cold but die due to leaning or going too rich when warmed slightly - I haven't seen this extreme myself but theoretically its possible. A friendly MOT tester with the kit could probably help out here as they can measure what its doing. Easily adjusted via allen key.

Lastly, it could be a sticky metering unit flap - millions of articles written about this (don't worry whether its xr3i specific - just K-Jetronic Metering Unit) so I won't repeat all that. If you try and rev it when its cold (and running), does it stutter, or does it rev cleanly and come back down to idle cleanly? If yes, then I'd doubt its this, but again its all easily checked and cleaned up.

 

To add - you say it doesn't kick or anything when cranking after its died. Have you pulled the plugs? Bet they are absolutely dripping wet! That will give you a good indication of which direction fuelling is going too

 

Thanks for the advice, I will check all that and see.

When the problem first started a few weeks ago it would die and start a bit sounding rough and I would have to keep revs up to keep ot running so as you say sounds like something to do with fueling. Now it just cuts completely after a few minutes even just at idle and no amount of coaxing will get her to even kick.

I will investigate further.

Prior to this it ran like a dream, long runs, hot cold.

 

Out of interest, when was the last time it had a fuel filter change?

 

Yes changed fuel filter couple of weeks ago.

 

A little update, let it run until it died this morning, took a plug out checked spark, none apparent. Put volt meter on dizzy, nothing coming out. I have already replaced the coil so I am now thinking it is the distributor possibly?

I shall try obtaining another one and see...

 

Hang fire on replacing the whole dizzee.
It will be the ignition module (black box) bolted to it. There is a heat paste between the dizzee and this, it dries out and then cooks the unit.

Usually once they've died thats it - haven't had one that allows ~5mins of running every time, but its certainly not impossible

 

 

An update for any that might read this, it is fixed.

I changed the whole distributor and it works again, in all liklihood it was the black electronic module on the side but i went for the whole thing. It is an easy job 2 bolts, just make sure you mark the position of the distributor on the dead, I drew round the outline. I also put a new little rubber seal an A smidge of sealant around the base to stop any oil leaking.

 

It will be worth getting a timing gun on, although hopefully its close, the internal springs wear at different rates and you might be running a tad advanced or retarded. For the sake of literally 2mins with the gun and swinging the dizzee one way or another it'll be worth it to safeguard the engine (and maximise your power with what you've got)

 

Does it suddenly stop running or does it start to run bad before it dies?