93 maverick duel fuel carbereted missing when at normal temp

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.

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?

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.

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Originally Posted by 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.

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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

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.

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.

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

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.

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.

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

just trying to get a broader base line on where the engine is at.
more info gives us more to chew over and offer you a solution.
9.5 v after resistor is low no wonder it didn't want to start.
hows the battery and alternator?.
and as bro taslucas said earths

check voltage at ignition you should have 12v.
at coil starting voltage should always be 12v and, after you release key with resistor slightly less.
helps to preserve points from burning to fast.
but the pertronic modual is designed to run with oem type (resistor) coil.

putting the coil issue aside hows the plugs and leads.

Bit more info for has, trip home was great, only missed a couple times. Climed the Adelaide hills 10 km very step no worries. A little cough and backfire at the top of the hill on gas. Ambient Temperature was 22. Started to miss a little about 1.5 hr's into trip, ambient temp 26. Pulled over for a coffee and 20 min snooze. No worries all the way home.

Still lacks a little power so I've got new plugs. Colder ones and gaped them to 0.7mm as per ngk instructions. See how it runs tommorow on the trip back to the big smoke ( 4.5hrs of hard rock music)

I had similar problems.

Removed the ballast resistor and changed the coil to a gt40 - still intermittent misses.

Found the advance ring in the dzzy was seized - cleaned and greased it - qworking properly.

Redone all the wiring connections as I found suspect crimped connections at the coil in particular the wiring going to the gas safety switch - fixed.


With the changes Im now getting better fuel economy.

Signs are good, replaced the plugs with colder ones set to smaller gap, truck hasn't run this good since I got it. Doesn't hessite after stopping at lights, more power too. Old plugs looked fine when I pulled them out 2 weeks ago but today they definately showed signs of running too hot. Gap was also too big, close to .9 mm which the book says is fine for standard (.8 to .9) but ngk website said too big for gas. Haven't tried it on petrol yet.

Yeh I thought my advance ring was not working, degreased it and lubed it with high temp grease, if I duck on the tube it was working fine. Tried with and without resistor , no difference. Was worried volts might be too high without, 13.4 volts when at idle. Now its at 11.4 at idle.

Attachment 42936 the old pugs all show too hot like this.

Good to hear you've got it sorted mate.
I mat check up on my dissy advance too cheers

Thats good news.
Keep an eye on plugs gap std type plug will wear faster than normal with lpg.
recon 5000 klm is good base line for rechecking plugs
Thats why I suggested use Iridium.
Ive had em for 5 yrs now, wear wise never had to clean or re-gap em once due to k's.
to me that truly "electronic set and forget", as it should be in a perfect world lol.
and that's not a fluke I run in in my GTR also same good results they are even older and higher k's.
If ya get the odd miss still on lpg, gap prob still the slightest bit large.
sometimes it can take a few goes to find the optimal gap setting.

Seeing that it had incorrect plug gap from previous owner,may indicates state of overall tune
Might pay to take it to lpg tuner for a going over..
that way you will have peace of mind things are as they should be.
tell him Iv'e gone over it,plugs timing is ** deg, etc etc think its ok, and I want my tune checked.
(after a second opinion so to speak).
he may check for lpg leaks & then put his exhaust analyser on it and set about his business.

Also does it have a upper cylinder lube system fitted like morreys?.
cheers

Doesnt have cylinder lube system.

All so update from the big trip. Ran sweet for 1 hour, few misses, but not too serious. Stopped and fueled up. Ran good for another hour, then few misses, bit more than before. Pulled over for dinner, got timing light out ( bough a new one on Saturday but hadn't used it yet). Found timing to be advanced buy 15 degree. (this thing was serviced by Repco mt gambier for last few years). Adjusted to 11 degrees. Ran great for next 2 hours, no misses, power seemed a little less tho. Missed quite a bit driving through the Adelaide hills ( very winding and up and down steep hilly, great if I had a skyline, bit hairy late at night in a maverick). Wondered if it might be running a bit lean on gas, and that was making it run hot?

try 12 deg.

yeah more advance is good off the mark, but you lose top end.

duel fuel advance is a compromise between the 2 fuels.
lpg can go even higher adv, but petrol won't like it so under 15 deg is sorta best world.
if your running hot might pay to service cooling system.
plenty of threads on that.

but sounds like you had a win to me.
cheers

Well thought all was good till last week. Problem back but not as severe. Mostly has issues with start and idle at lights on both fuels. Drives OK when warm. last night in desperation to start I was squirting some startyabasterd down its throat and noticed it wasn't going down into the intake, looked down into the carby, omg, full of crap. Got a kit today but now I need instructions, my Haynes book doesn't have any. Sigh. Missing my old ranger at the moment.

Take photos of the carby - before you remove it from the truck - note where the vacuum hoses run

Take photos of the outside of the carby in particular the side whee the acc cable is - you need to note the position of the fast idle cam

Pull the carby apart over newspaper (there as some little ball bearings that may cause you grief)

Clean everything with carby cleaner

Dont use any sealant

No good. Engine now starts OK but won't idle properly. Too fast or too slow with little adjustment. Sigh. I'm sure its a choke issue and the deceleration unit is faulty too. Thinking of going dedicated gas and ditching the Carb for a throttle body. Or I'll just get a reco carby when I can afford it.

I have this exact same problem I was also told to put in a thermostat that runs a few degrees colder haven't tried it yet going to get a manual first.

It kind if makes sense to me since it doesn't happen till full operating temp.

Is it playing up on both fuels as the idle ise set on the converter with LPG

I take it you put the kit though the carby.

Is the fast idle cam in the correct position -

Have you gotten anywhere on this?.

I was reading through the manual and found you should change the condenser every time you put in new points is it possible that needs to be changed as well?

Replaced my leads and put in a extended rotor button has come up alot better no more carby backfires :).

Still a slight miss at idle now that its only at idle going to do the valves see how that goes.