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Old 04-27-2018, 02:31 PM
irishjedikev irishjedikev is offline
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360 2100 Warm Start Problems

Hey Guys,

Really need some help here. I have an issue that I've been trying to deal with with no luck at all. I have a 1975 Cherokee 360 with the Motorcraft 2100 2bbl carb. For some reason, she doesn't want to restart when warm. Starts fine when it's cold. Runs fairly normal until i shut it off. If i let it sit for about 10 min, forget it....won't fire until the jeep is cooled off again. The starter cranks fine and the battery is charged. Here is what I've already tried:

- Changed coil and resistor (no change)
- Rebuilt carb twice (no change)
- Replaced plastic float with a brass one (no change)
- Adjusted float both directions (no change)

I should also say that this did not come on gradually nor was it associated to change in weather. It was fine and then one day, this started. SO frustrated. I bought this jeep for $3k, put in another $3.5k in repairs and countless hours of my own fiddling and I've driven the girl maybe 60 miles since i've owned her. Please help if you can....I'm desperate! Thanks in advance!
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  #2  
Old 04-27-2018, 03:17 PM
irishjedikev irishjedikev is offline
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I should also add that the choke appears to be working correctly. With the air filter off, I can see that it's open when warm and closed or partially closed when cold.
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  #3  
Old 04-27-2018, 03:40 PM
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Don S Don S is offline
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..

The first step is priming it. I rigged a hose from a squirt can to the bowl vent. As I recollect there was two different types of power valves in those 2100s.

Dang I've forgotten more than I ever knew.. Don S..
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Old 04-27-2018, 04:46 PM
irishjedikev irishjedikev is offline
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Hi Don, I'm clearly not on your level, but i'll get there...some day.

I'm not sure i'm following. Priming what exactly? Also, this hasn't always been a problem...just something that has started happening. Are you saying that maybe the new power valve is not working?

I will say that both the carb rebuild kits i bought had 2 very different looking power valves. One looked like the book (which is the one I have in there now) and another one that looks like it has only half the valve and looks nothing like the other. This one has a flat top and an open bottom where as the one that's in there now has a cap on the top that unscrews and you remove a large spring and small brass cap on the inside that covers another small brass part that i'm assuming is part of the valve itself.

Any of this make sense?

I've seen lots of posts where people are talking about percolating and exhaust baffles, but not much on what to do to fix those things. Hoping someone knows. Thanks all!!!
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Old 04-27-2018, 05:04 PM
Ristow Ristow is offline
 
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the larger looking PV is a dual stage. the half size looking one is a single stage. if you tooke the other one appart as you described its now pretty much junk. i like single stage units better.

how is acting when it wont start. just cranks and cranks without even firing,or does act like its flooding. you need to verify the choke pull off is working. also,the choke should stay locked open until the throttle is pushed,even when cold. check that too.
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  #6  
Old 04-27-2018, 07:54 PM
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hey,does anyone here know how to.......
 
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is there a insulator between the manifold and carb thats missing? probably not since the symptoms are new.... unless this is a new rig you bought in winter and now its gettting warmer?

if you crank and no start is one of the plugs wet with fuel?

perhaps trying a electric fuel pump? might also it be a case of DISPO fuel line routing?

I have heard of...issues where the fuel filter was not in the correct position ( i think small line at 12 o'clock and the big line at 6 o'clock? but i dont know if you have this on your year rig - i only know 86+ and up...sorry

i dont know much about carb vehicles as both of mine are fuel injection....

trip
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Last edited by Tripwire : 04-27-2018 at 08:01 PM.
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  #7  
Old 04-27-2018, 08:16 PM
irishjedikev irishjedikev is offline
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Thank you all for trying to help. So I just changed the 2 stage over for the brand new single stage. No change.

Somebody asked how it was acting when it won't start. It just cranks and cranks...kinda like if it was flooded. I do try pushing the pedal to the floor...still no start.

Spacer is there...appears to be about a half inch thick or so. There is was in the float bowl...still no progress.
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  #8  
Old 04-27-2018, 09:45 PM
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ZackN920 ZackN920 is offline
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Stupid basic question but...
When you start it after its ran, do you hold the pedal down a bit? not pump it, hold it, at around 1/4 of the way down?

That always helps start a carb'd engine thats been warmed up and no longer using the choke. It also really helps if the carb is a little on the lean side or has the idle speed screw set a bit low.

With how I set my carb up, my engine will not start after sitting for a bit with out some throttle action at start up.
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  #9  
Old 04-28-2018, 01:10 PM
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thumperjohn151 thumperjohn151 is offline
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Quote:
Originally Posted by irishjedikev
Hey Guys,

Really need some help here. I have an issue that I've been trying to deal with with no luck at all. I have a 1975 Cherokee 360 with the Motorcraft 2100 2bbl carb. For some reason, she doesn't want to restart when warm. Starts fine when it's cold. Runs fairly normal until i shut it off. If i let it sit for about 10 min, forget it....won't fire until the jeep is cooled off again. The starter cranks fine and the battery is charged. Here is what I've already tried:

- Changed coil and resistor (no change)
- Rebuilt carb twice (no change)
- Replaced plastic float with a brass one (no change)
- Adjusted float both directions (no change)

I should also say that this did not come on gradually nor was it associated to change in weather. It was fine and then one day, this started. SO frustrated. I bought this jeep for $3k, put in another $3.5k in repairs and countless hours of my own fiddling and I've driven the girl maybe 60 miles since i've owned her. Please help if you can....I'm desperate! Thanks in advance!
irishjedikev 230 Tornado
I know this is an old thread - Are you still having this problem?.
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  #10  
Old 04-28-2018, 01:28 PM
irishjedikev irishjedikev is offline
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Not an old thread at all and yes I'm unfortunately still having the problem. Any help is appreciated!!
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  #11  
Old 04-28-2018, 03:19 PM
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I haven't reached a level yet…

First open the hood, pull the air cleaner off.
Now while looking down the throat pull the throttle linkage. If you see a mist of fuel it means
A. There is fuel in the bowl.
B. the accelerator pump and the fuel pump are indeed working.

If not…

Priming basically means feeding the engine gasoline or carburetor fuel before using the starter.
It is dangerous but many just pour an ounce or two of fuel down the throat while another cranks the engine. The engine can back fire through the carburetor. This can singe your eye lashes or worse!
BTW worse is set the fuel you're holding in your hand on fire. you drop it, then you have to buy another truck!

Most carburetors have a tube in the throat that acts as a vent to the bowl I put four ounces of fuel slowly into the tube if I think its empty

I started to learn this car stuff in 1948. Now I gotta do it all over again.

Good Luck.. Don S..
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  #12  
Old 04-28-2018, 03:23 PM
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Get/use a can of starting fluid, easier and safer.
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  #13  
Old 04-28-2018, 06:01 PM
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thumperjohn151 thumperjohn151 is offline
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Irishjedikev -

OK - in your original post you said "this came on suddenly" & "Runs fairly normal" (I think...) when its warmed up to normal temp.
So back to basics:
1 - Have you checked for vacuum leaks - "the old carb cleaner squirt test" - check along the Valley where the intake meets the heads -
check the base of the carb-to-manifold (I read you've had the carb off/on - just sayn')
check any/all vacuum lines/connections

If it fails, chase that -
If not check this:

"this came on suddenly"
Does your setup utilize an EGR valve?
The port(s) get crudded up with schmutz, and SOMEtimes... a piece can break off and jam the valve open - doesn't take much, but you have a vacuum leak between the exhaust/intake - runs, but like s#$t. AND hard to start warm... Unfortunately, I think the only way to test this is to pull it and bench it.

Lastly (for now, anyway..) How's your compression..?...
Rich start vs. Lean start - low compression will give you grief, but not "suddenly"...

OH YA! How's your breaks? Vacuum leak in the power booster (Ruptured diaphragm)
Leme know, what you know, when you know...
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Last edited by thumperjohn151 : 04-29-2018 at 09:46 AM.
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  #14  
Old 04-28-2018, 10:32 PM
irishjedikev irishjedikev is offline
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Wow guys!!! Thank you all so much for trying to help me out of this mess. I can't tell you how frustrating it's been.

I'll try and address the latest posts....

I have not taken the top of the carb off immediately after it won't start, but I have shortly after and many times with the engine cold. Every time i have taken the top off, there has indeed been fuel in the bowl.

Regarding the accelerator pump...i have manually activated the arm and witnessed fuel squirting into both barrels. Pump appears to be working well. Don...I hope your story was only true for the burnt eyebrows!

Tony, I will buy a can of starter fluid.

Now onto thumperjohn's ideas...

1. I have not checked for vacuum leaks. Good suggestion. I will try this tomorrow.

2. I believe i do have an EGR valve, however my mechanic removed the hose between the carb and the intake. Right now both ends are capped off. He claimed he did this because he was afraid the EGR was contributing to a rough idle.

3. The Jeep runs good while it's running. Just won't restart. The only driveability issue I notice is she does hesitate just for a second when you jump on the accelerator. Almost like it wants to shut off and then it catches up and takes off.

4. I have not checked compression at this time. The $3.5k I spent on repairs went to addressing leaking manifold, machine work on the head, and a bunch of other smaller things...one including the first carb rebuild. I did the second myself.

5. Brakes are great. They squeak a little, but stop fine, brakes evenly, doesn't pull one way or the other.

Funny side note...the moment this started, I was actually at a shop picking up a replacement QT. Is that the life of an FSJ owner or what?!

My wife has been more than cool about all this, but to spend this money and not be able to enjoy it is killing me. Really appreciate all the support. Don't give up on me! I will pickup some starting fluid tomorrow and start spraying it around the base of the carb where the spacer is. I think I have a compression tester someplace. If i can find that, I'll do that tomorrow and let you know.

Lastly, if you guys need pictures or anything, let me know and I'm happy to post.
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Old 04-29-2018, 10:14 AM
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thumperjohn151 thumperjohn151 is offline
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1. I have not checked for vacuum leaks. Good suggestion. I will try this tomorrow.
DON'T USE STARTER FLUID for the vacuum leak test!!! Carb or Brake cleaner only please!! sorry, didn't mean to YELL - saving your eyebrows (and the rest of your Jeep :-) )

2. I believe i do have an EGR valve, however my mechanic removed the hose between the carb and the intake. Right now both ends are capped off. He claimed he did this because he was afraid the EGR was contributing to a rough idle.
If its leaking at idle, that's a problem - it should only kick in on sudden deceleration - it should be totally closed at idle -

3. The Jeep runs good while it's running. Just won't restart. The only driveability issue I notice is she does hesitate just for a second when you jump on the accelerator. Almost like it wants to shut off and then it catches up and takes off.
That's weird, because you've rebuilt the carb twice now - this is symptomatic of a bad/clogged accelerator pump, and/or a vacuum leak -

4. I have not checked compression at this time. The $3.5k I spent on repairs went to addressing leaking manifold, machine work on the head, and a bunch of other smaller things...one including the first carb rebuild. I did the second myself.
OK - head work would eliminate compression problem...

5. Brakes are great. They squeak a little, but stop fine, brakes evenly, doesn't pull one way or the other.
So they act like Power brakes and not manual - peddle is "easy" to push, didn't all-of-a-sudden get harder...?...

And anyone else reading this thread PLEASE chime in on my thought process - I've left a lot of details out...
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Old 04-29-2018, 11:20 AM
irishjedikev irishjedikev is offline
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Hi thumperjohn and all. So I just went outside, fired it up and sprayed some brake clean....no change in idle at all. I sprayed the base of the carb and any vacuum hoses i could find. nothing changed. Maybe the issue is more related to when it heats up so i'll try that next. It's running in the driveway now....i'll get it up to temp and spray again. Wasn't paying attention and the bottom of the brake clean can hit the fan! That will wake you up! (for headscratchers out there, i am missing the fan shroud so the dangerous parts are all exposed!)

There is one thing i found though that looked suspicious. Found a vacuum line just sitting on top of the valve cover on the drivers side. Sprayed it with brake clean and nothing happened. Traced the hose to what looks like a valve on top of the intake right next to the coil (just to the right if you're looking in the engine bay. I found a t connector with one inlet capped off. I assumed that's where this hose went, so I got brave, took the cap off and plugged in the loose hose. Nothing happened, but maybe it has something to do with it? Though for sure the EGR was on the back. That makes 2 valves on the intake that are either capped off or not connected. Seems odd. Gonna look at the book and figure out what is what. Not sure why he (mechanic) would not want any of these things hooked up.

Just to recap....there are now caps on a valve behind the carb on the intake and a cap on the carb on the passenger side. Had a loose hose that went to some valve on the front of the intake and I plugged that into an open spot on a t connector right next to the fuel filter...hope that was right . Jeep running in driveway to heat up. Stay tuned......
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Old 04-29-2018, 11:32 AM
irishjedikev irishjedikev is offline
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Ok....jeep now up to temp. Before I turned it off, I sprayed again with brake clean and nothing happened. Just to test the brake clean, i sprayed some with into the air intake on the air cleaner and the idle did drop! So proof of concept is solid....just no leaks around the carb or near any of the vacuum lines. jeep is sitting at the moment and then i'll try to restart and let you know if that loose hose had any affect. In the meantime, I'm gonna go through the shop manual and make sure i know what valve is what.

No explosions yet (thanks to you!) Will try and keep those to a minimum if possible!
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Old 04-29-2018, 12:01 PM
irishjedikev irishjedikev is offline
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Ok....

No change. Still won't start. Very close to giving up on this thing.

I did learn a couple things though. First, I found the EGR valve and that is not capped like i thought. The hose is just sitting loose on the passenger side valve cover. The thing that is capped on the back of the intake looks like some kind of sensor with an nipple on it. That has a cap on it. Not sure what that is.

The inlet capped on the carb appears to be where the EGR hose would go. Should I cap the EGR? Plug it back in? Leave it loose?

Also, is whatever capped on the back of the intake of any importance?

Onto the front of the intake....

There appear to be 2 sources for vacuum hoses. There is a sensor on the passenger side right near the coil. 1 hose coming from there that was just sitting loose. I plugged this one into an open inlet on a t fitting near the fuel filter (not part of it...just near it). Finally there is some kind of sensor/valve on the drivers side of the intake near the front. This has 3 hoses coming out of it which all appear to be connected.

Seems like i'm going nowhere fast.
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  #19  
Old 04-29-2018, 12:05 PM
irishjedikev irishjedikev is offline
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Frustrating thing is....all these hose issues while certainly concerning doesn't really explain why it was fine for a while and just suddenly started acting up.

Would a new/different carb help? I have no idea what's happening with this thing.
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  #20  
Old 04-29-2018, 01:45 PM
wiley-moeracing wiley-moeracing is offline
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Stop now! everyone is assuming its a fuel issue, check you ignition first! You need to check for spark at the plugs. sounds like your ignition module failed, check pick up in distributor, check coil. Do this before moving onto anything else.
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