93 maverick duel fuel carbereted missing when at normal temp

[munzy42]

help. 93 maverick 4.2lt. Duel fuel, carby. Pertronix lobe points replacement. Gt40 coil (without resistor type). Issue I have is miss developes after 15 - 20 min, once everything gets hot. Doesn't matter whether its on gas or petrol, gas is worse than petrol once problem starts but truck runs sweet on gas or petrol to start with . I've fit a new coil, cleaned terminals, checked/cleaned plugs, I'm getting 11.3vt at + on the coil and earth lead on distributor base when running at idle ( tested when problem pressent) . Today was a cooler day and magically the truck ran good for the whole 25m drive home. ( slight miss at take off if idling at lights for a minute or two but then OK)

When it played up yesterday I cracked it and pulled over to test power ect, sat in the truck reading the manual for 1/2 hr with engine off then it ran fine for 15 min again.

think its a spark issue because it happens on both fuels.

[Robo]

what brand spark plugs.
duel fuel NGK is my choice.
and Iridium at that.
don't need to worry about heat or gap for a very long time.
expensive and worth it, m2cw.

What is the plug gap set at, lpg likes .2 less gap.
ya could even need a little less.
and lpg timing need more advance 12-15 deg for duel fuel.

From memory Pertronic should run with resistor coil, it may be damaged and be the gremlin your chasing.

how old are the leads?

[munzy42]

Are you saying the pertronix module could be failing after 15 or 20 min. I kinda wondered if the module was dodge, but I thought it might be one of those devices that either is or isn't OK? And seeing as the truck runs great when cool I thought it mustn't be the module. But then I second guess myself and crawl into ball crying cause I don't really know.

[Robo]

Are you saying the pertronix module could be failing after 15 or 20 min. I kinda wondered if the module was dodge, but I thought it might be one of those devices that either is or isn't OK? And seeing as the truck runs great when cool I thought it mustn't be the module. But then I second guess myself and crawl into ball crying cause I don't really know.

not stating it's the problem, just fyi,
just recal instructions stating run with resistor.
I'm certainly no electronic wizz, but if something needs resistance , well you do the math.

to me your problem sounds both a little electrical l& fuel mixture.
don't soob that aint fixen it.

oh lpg wants 1 range cooler plug.
hows about some Info of where the engines at, whats what parts wise.
when did ya last check compression.
has carby ever been overhauled etc etc.
Its easyer to help diagnose

[taslucas]

Hi munzy. Yep it may be that the pertronix has failed. I had a pertronix 2 (hall effect) module and it was faulty out of the box. The symptoms were exactly like you described. It started missing after 10 -20 minutes.
Also a faulty coil can produce the same symptoms. An easy test would be to swap the coil with someone that has the same just to isolate that problem.

I uploaded test instructions for the pertronix2 module(hall effect) Not sure if that's the one you have though. You can find them in the manuals section.

[munzy42]

Hmmmm, OK I'll have look for that test procedure then. Mines a lobe sensing style. Do I need to test it after its starts playing up or anytime.

[taslucas]

Not sure about the lobe sensing units. With mine it was done with the distributer cap off. So not while the vehicle was driving

[munzy42]

So it was nice and cool today again and the truck ran good to and from work. Missis a little at takeoff from the lights once it comes up to temp. I've bought a points and condensor to replace the ignitor module if the problem occurs tommorow on the way home. 5 hr drive from Adelaide to Mt Gambier. Hopefully I won't need them.

[munzy42]

Did a compression test 2 weeks ago while trying to get truck to start after it ran really rough the night before and wouldn't go at all the next day.

9 to 9.5 bar across all. When cold.

Spark was intermittent and weak looking, so I cleaned the rotor, cap, plugs ect. Still no start, bought a new coil, still no start, voltage to coil was 7.5 vt after resistor, resistor 1.5ohm so I bypassed, voltage 9.5 at coil, still no start. Cracked it, had a coffee, watched some telly, came back out to pack up tools tried it again, started no worries. Seemed to run OK after that but trips where less than 15 min long.

Don't know when carby last serviced, only had the car 4 weeks. Autopro mt gambler were servicing the truck every 5000, not due for service for 3000 more k

Not sure how it could be the carby causing my issues as the problem is identical on gas and petrol.

[taslucas]

Yeah it sounds like a spark.issue but looks like you've covered any coil problems.
Maybe obvious but perhaps check all wiring especially earth?
If you replace the module with points then you should be able to isolate that as a problem or not