Greetings all, First time poster, short time lurker.

Back in November I bought a very used 91 F-150 S/C 4x4. 240K Km on it so she's about done. She was dual fuel Gas/Propane.

Its a garbage scowl/ home repair parts hauler so no life time expectations.

Now, Im in IT but grew up on a farm so I have some mechanical skill ect but not nessicarily the training or the know how.

Background:
Any way, when I bought it it needed new brakes, no worries, all new rear, from the porpotioning valve back, incl. park cables.

Since then I've been having problems with the propane, and tryed to fix the gas system. Long story short is the gas is shot, would have needed new injectors, pumps, and tanks (leak). so its now SINGLE fuel. I have repaird the propane system and discovered that most (all) of the problem was low coolant.

More recently she started using 2 GAL of water for 60 Mi. No leaks were evident and it pressured up ok. I came to the conclusion that was a head or intake gasket and tore it down. No gasket blowouts noted, however the heads were screwed up from running propane. I got a set of Windsor heads (apperently off a 302) for it that were rebuild for propane (stelite seats and sodium filled valves) and only had 20K KM on it (where his bottom end blew up...)

Reassembly uneventful, repaired screwups as nessicary (striped out 1 roker arm bolt hold, heli coiled all good now). No extra parts

Starting super bizatch. Located 1 mix up on fireing order and determined distributor out by 1 tooth. Starts hard, idles rough (500rpm) power seems good and it all smooths out with throtle to 900 RMP. sounds like it could be missing on 2-4 cyclnders though. While idleing the computer seems to be seeking as it will cycle through missing, good, and pinging.

I've nearly eshausted my know how and analyitcal skills and would like Ideas.

From reading on the internet I can tell that I need to redo the timmin with out the computer. I see there is a plug I need to disconnect (SPOUT? is it that little 2 wire bridge on in with the distributor harness?)

Also I read that some of the 302 were blessed with a 351 cam... is it in my interest to try 137 order? I also see that there could be routing issues with 7,8 that I will address.

Also just a note, when I messup the distributore position it was setup so that the rotor was centered on the #1 position, the way it is now is very late, almost off the contactor but it does run there. any other position = no run. I asume that reseting the crank position is part of the timming.

Any other Ideas?

PS talking to the previous owner (co-worker) its always idled ok, ran good, and been hard starting and low on the power (hard on gas) since he converted to propane.... perhaps the guys that did the conversion messed something up in the timing originaly?

 

add: kind of sounds like the opposite of :https://www.ford-trucks.com/forums/7...e-of-ford.html

as once your at speed all is good.

will check TPS, ERG, and the coffe can in addition to timming issues. While checking the water problem the hard starting and rough idle problems started. Directly related to me allowing vac line to coffee can to melt to EGR pipe. I think I fixed it by sliding plastic line ends coated with forma gasket into rubber vac line.

Also: it got new spark plugs, cap and rotor. New spark plugs are hotter than OEM to keep the propane from burning them up. Autolite 26 vs 24.

 

add also:

All Gasoline fuel system components have been striped out, injectors, rail, tanks, most of the fuel lines. Holes in intake filled with pipe plugs (tapped in), and teloned. FPR vac closed off, and sealed with forma gasket.

A/C system removed, it was dead and in the way. compressor kept to keep same belt.

More reading leads me to check the IAC and the air pump lines, in additon to the EGR pipe. Question how do I check these?

 

I went through after our thunder storm and got the timming redone, its right where it should be. 15-20 degrees. Still misses like a SOB at idle. Also never did find the SPOUT connector so I set it best I could with the computer running the show.

vac canister holds pressure (unpluging it after engine stops results in loud sucking from the can.)

chased around the spark plug wires fireing order still looks right... 7&8 spererated.
close wires were given some wire loom to keep them appart.

no arc's or sparks in the dark (or blue cables). new set of wires on hold at shop anyway.

I see that mcfaddendrafting got his rig going. and pinned it down to SP. I have an extra set of colder plugs for this thing so I'm going to try them in the hole(s) that are missing (when I figure that out).

will also look at compression.

I'm not going to be chasing any sensors until the missing is solved as that seems to be the problem.

 

YOu should be able to pull the spark plugs and tell if the cylinder is firing. A good plug should have a brown look to it, a missing cylinder plug may look un used.

 

You'll never get the timing set correctly without pulling the SPOUT. It's a gray plastic plug near the distributor or near the firewall on the driver's side. Even at idle, the computer can add 5-15 degrees of advance, so if you set the base timing with the computer still in the loop (SPOUT not pulled), you're way off.

Jason

 

alxsnmr, spark plugs have less than 5 km on them. I haven't left town with it running like it is, and have barely warmed it up sitting idle.

jroehl, I know this, but atleast I know I've got the distributor in the right range . and your post tells me exactly what to look for! it looks nothing like whats in the book (1 wire near firewall). one wire pffft, ive gota 2 wire dohickey hanging of the distributor harness that has a small grey plastic plug in it so thats got to be it then).

 

start the engine let it idle with a pair of insulated plyers pull one plug wireof at a time if the idle doesnt change theres is your miss. pull that plug and see what it looks like. I bought a bran new set of plug along with every thing else for a tune up and it turns out there was one bad plug in the set It drove me nuts but I finally found it changed it and its running like a V8 now

 

mcfaddendrafting, I read your post so I was thinking the same thing.

any how its going way more better now! pulled the plugs and only 2 showed any idication of running. 2 more looked like they may have been running and the remaining 4 were blotto.

thats way to many SP to be a defect unless its the whole lot. so I shot some ATF in each of the no go holes and now its way mo beta.

there may still be 1 missing, but its hard to tell with the exhaust leak.... (cant get the pass side manifold to mate up with the pipe.... )

found SPOUT and reset timming.... low and behold it's exactly where the cold chizle mark is from when someone prior to me set it.....

Drove it for 50Km no big problems (doh on cruise control check valve, fixed). Idle is very smooth, so I throttled it back down to 800, where it may be missing on 1 again as above.

She still very hard to start, more than likly due to the req. VAC build up to activate propane. just tinkering left now I think Ill send the wire set back as everything is good now and I need to stop the bleeding on this thing!

 

mother $@%$@ truck!

ran good all the way to work, ran good at work. Started right up at lunch (havn't had to time to fix that issue yet but what ever its warm and runnin....)

stop for lunch.... no start.

turning, sounds like low battery.
seems to go in fits and starts (the starter turning that is)
attempted boost, no help, did not draw any load of other truck.
wire from battery disconnect swtich to relay is hot as is wire from relay to starter. did not get at the wire from battey to switch..... will try to bypass the switch before throwing parts at it......

3 options, all cooked from messing with it to get it running.

1. starter relay
2. battery
3. starter

I say relay because the starter is turning, and boosting did nothing.

Idears or should I walk away......

 

It's definatelly not the starter relay, but are you aware that there is a solenoid mounted down on the starter ?

 

1st sorry for long posts, I'm using this as a blog (writing it out gets me thinking) and sounding board for my ideas.

netscaner.... Apparently I'm using wrong term. its a Fender mounted solinod that I'm calling a relay. The starter has only a + lug, and 3 bolt points that could accept -.

ok..... now it get strange....

4 hours later it starts..... get it home and for giggles retry turning it off and starting.... no start. sounds like low batt.

this morning i gets to looking at it, starts good, go to shop to consult with mechanic. restart no go.

battery proven to be good. that leaves relay(fender mounted soloniod whatever you call it) or the starter it self....

further trouble shooting shows that short time run periods do not affect this problem, only 5 min or more drive. 5 min idle (from hot)did not recreate problem.

I now have on hand the new solenoid(relay thingy) and a starter. Due to being unable to make it do this with any consistency to rule out parts I have not installed anything. Reason for testing extensively is to see if the ko-hershy switch is playing in to it.... but by the time I bypass it and retest the results have been different (inconclusive). Dont have the time to day to do a 20 km drive between cycles but it is likely to be what I need to do.


Now in the mean time an additional problem cropped up. on the way home it started missing again. rather than shoot more oil into cylinders(may do it again anyway) I actual looked at what was going on. results #4 worked it self unplugged.... not the first time this has happened (its much smoother now, go figure ). wire just wont stay on there.

It now has an intermittent miss. I cranked the hot idle up from 750 to 900, its better but still there. #1,7,8 seemed to have mixed results with being unplugged, first time no change, second time very mad, 3rd time good, the rest are consistent (good). I'm assuming that this is where the mystery miss is coming from, only thing I can think of is wire set (given that #4 wont stay plugged in to.) too bad they never actually ordered it other wise it would still be there....


and I'm sure that you guys are wondering why is he ordering parts he may not need then sending them back? 2-3 days to get here, ??? as to right part actually showing up (happens often enough that his supplyers don't charge him for it) etc etc.

 

Your problem is most likely the starter, ... heat up and slow crank is a common problem.
I thought your 91 was similar to my 1994. There is a big starter relay on the fender and a small wire from it going down to a solenoid mounted on the starter. And there is a seperate big cable going to the starter mounted solenoid.

 

I'd be curious as to how you're adjusting idle--it's not adjustable on these trucks (there are ways to change the idle speed, but that can goof things up and throw the computer off).

Jason

 

there's a set screw on the top of the throttle body that holds takes the slack out of the throttle cables.