Petrol system problem maybe. Advice needed please.

[Number 6]

This evening I encountered an issue with what seems to be the fuel system. The 80 is petrol & LPG.

On LPG it runs fine.

On driving away from work this evening it was misfiring badly, or gave the impression of misfiring. I got it warmed up and switched to LPG then back to petrol. The "misfire" had gone but accelleration was flat to the point of being non existent at all points until kickdown cuts in at full throttle at which point it takes off.

I've put a bottle of injector cleaner in and I'll run it on petrol as far as possible over the next few days to see if that helps.

If not the injectors what could it be? This problem hasn't gradually appeared, it was AOK this morning but not this evening. It's fine on LPG so I'm discounting plugs and the ignition system in general at this point.

Fuel pump?

ECU?

Or what? Any ideas?

 

[BRE Fabrications LTD]

Hey No. 6,

Have you or anyone else done any work on your motor recently?

I have had similar issues in the past, this turned out to be melted wires on the fuel injector loom. Not unheard of on the petrol 80's. What happens is that the injector loom runs very closely past the EGR valve pipework. This pipe get exceptionaly hot and can cause this:

This is where the loom can come into contact with the EGR pipework:

As you can see in the above pics, there are copper strands exposed. This causes the injector to "ground" to earth, when it touches the metal EGR pipe. This causes the injector to open which can lead to a flooding condition which could be the cause of your flat spot.

What type of LPG install do you have?

If it is a multipoint system the installer would have had to splice into your injector loom in order to get the signals required to operate the LPG injectors. The loom may have been compromised and in turn be more susceptible to damage from the EGR Valve.

I ended up cutting out the melted sections and repairing the wiring by soldering in new sections of wire with heat shrink tubing over the new joints. I then wrapped it in high temp self amalgamating tape followed by heat wrap for exhausts.

Hope this helps, otherwise check your leads, dizzy and coil.