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..Starting problems..

rob h

rob h

1/2 ton status
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Location
frackville,pa
I have a semi large , problem. First of ill tell ya what all involved, 350 .040 with 12:1 comp, Mallory unilite, rpm airgap intake, x450 propane carb with a x-1 evap, elec fuel lock off. I have replaced and gapped the plugs, new cap and rotor, newer 1000cca battery, msd 10mm wires.... It starts on the first try but when shut off it wont restart,(turns over fine and fast) just chugs. It it sits for a while it will restart. The propane tank is full, valve all open, the lock off clicks when turned on, I couldnt find any leaks, the coolant is topped off and full. When trying to start i smells like propane, making me think its getting fuel. The spark seemed a little weak tho..but im not sure how much it should have.


Would the ignition module do that if its building heat and not working correctly..? The evap doesnt seem to be freezing since it will run and drive perfectly. The coil gets warm but it always have(blaster2)

Let me know what you guys think, i wana drive this thing so bad....Helps greatly appreciated, ill be out of town till sat and wana get er running to use sunday.
 
im kinda having this same prob with a car at school. starts fine cold but after you turn it off and try to start it again it takes a while. and its a 350, .40 over, 9.5 comp with a big cam and single plane intake. ill let you know if we figure anything out.
 
my new truck does this. As did my old blue truck. old blues problem was after sitting a long time, the fuel bowl had a pinhole leak, and would leak all the fuel out then be dry when you tried to crank her over. I still havnet figured out what the bronze trucks problem is :haha:From cold start she cranks just fine, start on first throw of the key.
 
Propane likes a good hot spark, especially with high compression which that fuel likes. Make sure your ignition system is up to snuff, any weakness and you will have problems. Given your description i might suspect the ignition module or coil. You might want to compare the spark you get cold vs hot.

Rufus
 
Im going to try a new module and a coil today, ill let you guys know what i come up with.
 
Ok, so far no good. The ignition module and the coil didnt help it. I tried to start it before i changed them both and it didnt at all, then i changed both and still nothing. I took off the fuel lock off just to see it worked and with power and it opens and closes fine. I took off the evaporator, i opened it up and its all clean. Im running out of ideas here, i might try a jumper wire from the battery to the coil to see if the ignition wire is bad but im not sure if that will hurt my module.
 
OK, back up and think about it for a second. Its almost certainly got to be fuel or spark. Engine runs good, so probably not compression, or anything like that.

You have not absolutely ruled out spark, but you have at least lessened the possibility.

So consider fuel.

If it were a gas engine, you would pour a little down the intake to see if it would fire. Hard to do that here, but not impossible.

But, think about this. If you have a gas engine that will not start, and you smell gas you figure its flooded.

In this case, you are smelling propane........What if the heat is causing a pressure build up, which causes too much propane to get into the engine?

Doesn't even have to be a pressure buildup, just something about the heat causing it.

Try moving the wire to where you can get to it easily, or even add a cutoff switch to the lockoff wire inside the truck.

Next time it won't crank, crank on it for a couple of seconds, then disconnect or flip the switch and kill the lockout and try again.

If its "flooded", it should fire after a second or two and try to run briefly.

Not as long as a flooded gas engine will, because in that case you can have actual liquid gas in the system that it can run on for a few seconds.

Or, if you add a lockout kill switch, try cranking it with the switch off for a second, and then turn the switch on while cranking.

As for pouring gas down the carb, you can do that with this system too.

Get a propane torch, stick it down the throttle body and turn it on without lighting it.

Probably not enough to run the engine, but it should fire and try.

I have cranked and run up to 25 hp lawnmower and 4wheeler engines on a propane torch at idle.
Its great for when you have a dry fuel bowl on a Briggs engine, and it needs to run a little while to fill it up.
The air/fuel mix is already perfect, so it can run straight out of the torch.
Just have to be careful, because most of my torches are the autolight kind.

J.
 
Disappointing but Fordum has some excellent suggestions and they sound like they should be your next course of troubleshooting.

Rufus
 
I was just out, i tried the idea of cranking it and then turning off the fuel, cranking it then turning the fuel on and cranking it....no dice. Then i had someone crank it with the fuel on and tried adjusting the mixture. It tries to fire but i had to stop, my 3.5 hp power master starter is killing the battery, time to charge it. Im thinking that the mixture was too rich and was flooding it, how that sound..? Im going to charge it and see what happens messing with the mixture. Is there any thing to go by with that..?
 
Sounds like you are on to the problem. Personally I have no idea how to set the mix on a propane engine.

The problem is, why is it getting out of range when hot?

I know you said that the fuel kill solenoid is clicking, but is there a chance it is not stopping the fuel when it should?
Maybe a bad seal or something that is letting gas flow even when it is shut off?

Thinking about it a little more, there has got to be a pressure regulator on this system somewhere.

I'm not sure how the carb regulates the fuel mix, but I'm sure that like most carbs, it depends on a constant fuel "level" or in this case, pressure.

If the pressure is increasing when hot, the carb is going to "flood". Cranking back on the mix will fix the problem until the pressure changes again.

Which means when it cools off, it is going to lean out to the point it may not crank.

Is there any way to measure the gas pressure at the carb?

J.
 
Im charging the battery now, when its charged ill try it again. Im going to remove the lock off if i can just to see what happens. Also ill have someone crank it and play with the mix to see if it fires. I dont know how id measure the gas pressure, i was thinking if the mix was too rich it might flood it when trying to start. i see what your saying with it leaning out on me. ill just have to keep messing with it later, ill let you know what i come up with. My evaporator is super clean on both sides.
 
OK, did a little research. Found a place that does conversions, but mostly on small engines. Generators that sort of thing.
http://www.propanecarbs.com/questions.html

One of the questions was about no start.
Here is what they said:
Sorry about the font, it was copy and paste.
Problem:
Engine won't start or is hard to start.
Solution:
More starting problems are caused by over priming or dirt on one of the regulating seats causing gas to leak through. If propane or natural gas make up more than 10% of the fuel air charge, the spark plug will not ignite the mixture, it is too rich. Propane and natural gas require from 50% to 100% higher temperature to ignite a charge as compared to gasoline. The ignition must be in good shape. You might try changing the spark plug gap to around .025

Remember this is for small engines, so I suspect the .025 plug gap would not apply to a big engine with a hotter spark.
But it does show that the mix is critical and much easier to flood than with gas.

At another point they mention regulators, and say that the pressure is critical.

Another site told how carbs work. They basically have a little "air vane" in the intake that is hooked to a valve.
When no air is flowing down the intake, the gas valve is closed.
The more air, the more it opens the valve.
The adjustments you see are to set how much it opens per air flow. So if the pressure changes, the same amount of opening will release too much or too little gas.

Here is a site that explains carbs. http://www.propanecarbs.com/home.html

And here are pictures of what you are supposed to do with a converted truck.:eek1:

J.
 
Maybe my mixture was too rich and thats why its hard starting, it could be flooding before it gets to start. Too much gas and it wont fire..Battery is 50% charged so i should know soon.
 
I hooked the lockoff to a switch, (just like fordum said Thankyou) and if i crank it with the gas off then switch it on it starts. Then when hot if i shut the gas off then the ignition. When i start it i do the opposite i crank it then it spudders then switch on the gas, it fires right up. I have to play with the mixture some, that seems to be the culprit.


Im not sure what way to put it but it is flooding itself when its trying to start, maybe its the mixture thats part of that but something else is contributing to it.
 
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Sounds like you need to lean out the mixture for when the engine gets hot. The only problem is that the problem could end up being the opposite of what you are having now...hard to start when cold, easy to start when hot. Does this set up have a cold start system, such as a choke?
 
Not a cold start system and no choke, it has a cold start primer, i might get an electric one for winter time that i can hook up in the cab. I was told that propane compensates for that. When its cold it starts up almost like injected(before this start happening). It starts the same either way, cold or hot. Its basicly flooding itself.
I did some research and found out that either the lock off isnt opening and closing correctly or its a pressure seat in the evaporator that will bleed fuel and make it just crank. Im went to order a rebuilt kit and found that woodward makes the same exact piece as my x-1 and the whole evaporator is only 30.00 more for a whole new one. The electric lockoff is also real cheap so ill be replacing them both i guess. Then i should be all good, ill keep my stuff and rebuild it for spares.
 
rob h said:
It starts the same either way, cold or hot. Its basicly flooding itself, i did some research and found out that either the lock off isnt opening and closing correctly or its a pressure seat in the evaporator that will bleed fuel and make it just crank. Im went to order a rebuilt kit and found that woodward makes the same exact piece as my x-1 and the whole evaporator is only 30.00 more for a whole new one. The electric lockoff is also real cheap so ill be replacing them both i guess. Then i should be all good, ill keep my stuff and rebuild it for spares.
Click to expand...

OK, I thought from the first post, it looked like it was starting the first time in the day you tried it, but after the engine had been running for a while, it would not start then. This lead me to think the fuel mixture was rich enough for a cold start, but too rich for a hot start.
 
This was just real strange....I could smell gas real strong, ive read that if the gas takes up more of the air than it should it wont fire, if i cranked it then flicked the gas on it starts. It just started this and got worse to where it is now. I didnt know what to think, must of got dirt in it some how either putting it togeather, when it was shipped or being sloppy. The truck is a dirty mess under the hood. Im hoping that when i change this ill have it fixed and running good again. Im still using the cash from selling my carb and some parts so its not sucking the pocket yet...lol.
 
Make sure you have a good filter in line before your lock off or have an integrated one in the lock off. You would not believe the amount of crap your tanks scale off. My filter gets changed out every 2 years. They go in white and come out brown and a bunch of fine power sediment in the bowl.

Rufus
 
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