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AMC 401 runs only on starter fluid

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zeebo76 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote zeebo76 Quote  Post ReplyReply Direct Link To This Post Topic: AMC 401 runs only on starter fluid
    Posted: Jun/23/2022 at 6:57pm
I have a new-to-me Jeep J20 with a warmed-over 401 in it.  It sat for nearly 20 years in a field on a freshly-rebuilt engine that didn't get the chance to get broken in before the owner gave up on it due to ignition problems.  I flat towed it home the other day, and managed to get it to actually run today - throughout that process, I learned a few things.

One:  The  (Carter 9635SA) carb definitely needs a rebuild.  There's silt in both float bowls, I get nothing from any of the jets at any point in time.  That is on my to-do list.

Two:  It has a massive exhaust leak.  It smokes like a forest fire.

Three (most importantly to me at the moment): It will only run on starter fluid - NOT gasoline.

So, I'll discuss #3 some more, as there are some relatively important bits of information in there that I think the community would like to know in order to better help me out.

Here's how I have it set up at the moment:  The timing is set up in "ballpark" format, the choke is wired shut as the linkage was frozen up.  If I crank and use starting fluid it will run.  Poorly, as I haven't yet had the opportunity to time it properly yet.  If I try to use gasoline instead of starting fluid, it won't start.  If I try to switch to using gasoline instead of starting fluid once it's running, it dies.  I've run it a total of five times, for 5-10 seconds at a time, experimenting with various operating procedures.

(FWIW, after every time it runs on starting fluid, I pull a plug to check condition.  After watching Project Farms' video on starting fluid, my findings (an oily spark plug) are in-line with his findings that modern starting fluid has oil additives in it.  I'm not worried about scoring cylinder walls given that my plugs are visibly oily every time I pull them.)

I'm not concerned about the carburetor at the moment, as I'm bypassing it completely by injecting/spraying fluid directly into the throat of the intake.  I'm a bit stumped currently, as I get nice blue spark and the ignition temperature of gasoline should respond to that.  Could it be a timing issue?  I at least have it "dialed in" enough for it to run, PERIOD, but maybe there's something going on.

I'd love some second opinions from smarter people than me.
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mstrcrftr View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mstrcrftr Quote  Post ReplyReply Direct Link To This Post Posted: Jun/23/2022 at 7:07pm
If you have already replaced the ignition components (plugs, wires, rotor, cap points etc), problems one and three are related, replace the carb and fuel filter, blow the fuel lines clean, check the tank for rust.  problem two is going to either be 20 years of dust burning off and 20 years of gunk in/or on the exhaust burning off  OR you have an exhaust leak.  you didnt say in your post WHERE it was smoking from..
 let me know if i can help ya. 

Barney
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Post Options Post Options   Thanks (0) Thanks(0)   Quote zeebo76 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/23/2022 at 7:14pm
Originally posted by mstrcrftr mstrcrftr wrote:

If you have already replaced the ignition components (plugs, wires, rotor, cap points etc), problems one and three are related, replace the carb and fuel filter, blow the fuel lines clean, check the tank for rust.  problem two is going to either be 20 years of dust burning off and 20 years of gunk in/or on the exhaust burning off  OR you have an exhaust leak.  you didnt say in your post WHERE it was smoking from..
 let me know if i can help ya. 

Barney

1:  The tank is plastic, so no rust there.  The first thing I did when I got the truck is siphon all the nasty stale fuel out of that tank, but that doesn't matter, because

2:  I've got her hooked into a spare fuel can with new fresh gas, and have cleaned both removable elements of both fuel filters.  She's getting clean gas, and any new particles are being filtered out.

All of the ignition system components have indeed been gone through, and in fact I have a post here detailing a few of my ignition system woes before I managed to get it started today.

Still, a few of my original points still stand.  By spraying/pouring into the carb I'm bypassing it as a fuel delivery device.  It's a non-functional carb, but that shouldn't matter with the way I'm doing things for the immediate moment, as all I'm trying to do is...  Get it to run on gasoline, and not just starter fluid.

Also, it has a pretty sizeable exhaust leak on the passenger side, from both the downpipe flange and the manifold itself.  How could that change whether or not it runs on gasoline?

Edit:  Meant to put this in the original post, but thanks for the speedy response.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mstrcrftr Quote  Post ReplyReply Direct Link To This Post Posted: Jun/23/2022 at 7:24pm
starting fluid is many times more explosive than gasoline.  thats why it will start with it, when it comes out the end of the can, its in mist form and evaporates into a gas that can be ignited easily.  you need a lot more gas mist to start it.. a lot more..
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Post Options Post Options   Thanks (0) Thanks(0)   Quote zeebo76 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/23/2022 at 7:29pm
Originally posted by mstrcrftr mstrcrftr wrote:

starting fluid is many times more explosive than gasoline.  thats why it will start with it, when it comes out the end of the can, its in mist form and evaporates into a gas that can be ignited easily.  you need a lot more gas mist to start it.. a lot more..

I kind of figured that the "mist" aspect had something to do with it.  Makes me wish they made cans of pressurized gasoline just so I could do some testing with it right about now.

Pouring gas down the throat of the carb should still have some result, though, right?  I'm getting zero evidence of ignition.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mstrcrftr Quote  Post ReplyReply Direct Link To This Post Posted: Jun/23/2022 at 7:47pm
here is a suggestion.  pull all the plugs out of it.  do a compression test on it. you can usually get a tester at your local parts store for free.  just put down the deposit on it. 
if you have never done one before, let me know and i can walk you thru it.  its easy..
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Post Options Post Options   Thanks (0) Thanks(0)   Quote zeebo76 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/23/2022 at 8:10pm
Originally posted by mstrcrftr mstrcrftr wrote:

here is a suggestion.  pull all the plugs out of it.  do a compression test on it. you can usually get a tester at your local parts store for free.  just put down the deposit on it. 
if you have never done one before, let me know and i can walk you thru it.  its easy..

That's a good point.  I probably have some stuck rings.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Regamble1969 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/23/2022 at 8:19pm
Originally posted by mstrcrftr mstrcrftr wrote:

starting fluid is many times more explosive than gasoline.  thats why it will start with it, when it comes out the end of the can, its in mist form and evaporates into a gas that can be ignited easily.  you need a lot more gas mist to start it.. a lot more..

The importance of this cannot be overstated considering the situation. The volatility of starting fluid can mask a lot of problems. If it lit once on starting fluid but won't run on gas, the causes can be one of several but considering the precision of a carburetor vs pouring out of a can, you won't get to an answer until the fuel system is functioning. At least the carburetor. Possibly see if anyone has a carb you can borrow and just run fuel to it gravity fed from a coffee can (i have a setup like this for all sorts of reasons). It might actually run just fine on the right amount of atomized gasoline.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mstrcrftr Quote  Post ReplyReply Direct Link To This Post Posted: Jun/23/2022 at 8:41pm
another thing to consider is, its been sitting for a long time.  the cylinder walls are most likely dry and it wont hold compression until it gets a little oil.. the compression test will tell you that.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote zeebo76 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/23/2022 at 9:36pm
Originally posted by Regamble1969 Regamble1969 wrote:

Possibly see if anyone has a carb you can borrow and just run fuel to it gravity fed from a coffee can (i have a setup like this for all sorts of reasons). It might actually run just fine on the right amount of atomized gasoline.

I'll probably just have to rebuild the carb myself - another first for me!  You could be right, and I just need more gas, in a finer mist, to make it work.

I'll be borrowing a compression tester tomorrow, and taking down some numbers.  Then I'll do the 'ole "seafoam in the spark plug hole" trick over the days after that to see if that improves anything, especially if the compression test numbers come back worryingly low.  Then I can pick up a carb rebuild kit and hopefully un-gunk whatever's gunked up in there, plug it all up again, and try once more.


Edited by zeebo76 - Jun/23/2022 at 9:38pm
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