Stumble
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Elder User
Joined: Oct 2016
Posts: 712
Likes: 1
From: Mesa, AZ
Did more digging and that was it. whoever rebuilt this carb last time installed the accel pump diaphragm backwards!
switched it around and instantly better throttle response. but now I do have a vacuum leak on the driver side along the base gasket....grrrrr!!! done for today. dont feel like working on a hot engine anymore. at least I am making progress.
also swapped another speedo in...second time doing this. this one seems to work good. addressed some wiring issues too and tracked down a couple bad grounds for my tach and lights. lastly, since I have a small Grabt steering wheel, I shortened the turn signal stalk so I quit accidentally hitting the signal all the time. good day I guess.
switched it around and instantly better throttle response. but now I do have a vacuum leak on the driver side along the base gasket....grrrrr!!! done for today. dont feel like working on a hot engine anymore. at least I am making progress.
also swapped another speedo in...second time doing this. this one seems to work good. addressed some wiring issues too and tracked down a couple bad grounds for my tach and lights. lastly, since I have a small Grabt steering wheel, I shortened the turn signal stalk so I quit accidentally hitting the signal all the time. good day I guess.
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
Did more digging and that was it. whoever rebuilt this carb last time installed the accel pump diaphragm backwards!
switched it around and instantly better throttle response. but now I do have a vacuum leak on the driver side along the base gasket....grrrrr!!! done for today. dont feel like working on a hot engine anymore. at least I am making progress.
also swapped another speedo in...second time doing this. this one seems to work good. addressed some wiring issues too and tracked down a couple bad grounds for my tach and lights. lastly, since I have a small Grabt steering wheel, I shortened the turn signal stalk so I quit accidentally hitting the signal all the time. good day I guess.
switched it around and instantly better throttle response. but now I do have a vacuum leak on the driver side along the base gasket....grrrrr!!! done for today. dont feel like working on a hot engine anymore. at least I am making progress.
also swapped another speedo in...second time doing this. this one seems to work good. addressed some wiring issues too and tracked down a couple bad grounds for my tach and lights. lastly, since I have a small Grabt steering wheel, I shortened the turn signal stalk so I quit accidentally hitting the signal all the time. good day I guess.
Laughing Gas
Joined: Apr 2016
Posts: 858
Likes: 118
From: Buffalo NY
Good info on the 2150.The Ranger Station Technical Library Index - Showing You The Way Since 1999!. search: 2150
Thread Starter
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Elder User
Joined: Oct 2016
Posts: 712
Likes: 1
From: Mesa, AZ
Ha was going to reply that the pump was backwards and the pin foes down for the lever to ride on to your last post, but you figured it out. So it was an accelerator pump issue all along. You are using a new thick gasket under the carb ? There should not have any vacuum leaks if you are using that gasket.
Wouldn't think so. I also replaced the paper gasket under the spacer since I had it all apart anyways. Guess I should have left it alone. Not sure which one is leaking.
There's no "This side up" on the thick gasket, is there?
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
It "should" not matter. Some were stamped with this side up but they were composite gaskets with a harder material on the bottom to seal to the intake/spacer, but I have not seen one of those since the 80's, I think they moved away from those decades ago. If it is not marked it will not matter.
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Elder User
Joined: Oct 2016
Posts: 712
Likes: 1
From: Mesa, AZ
I am ready to shoot my truck at this point. There seems to be nothing I can do to address this throttle hesitation. Vacuum leaks addressed, new parts in the carb...accelerator pump diaphragm was backwards. It's right now and the truck is still stumbling when I try to accellerate like anyone but a grandpa. It will pull all the way to redline if I give it less than half throttle but if i give it more throttle than that it falls on its face, and then goes. I have a lot of $ in parts on order for the suspension thinking this shouldnt be hard to fix but it has outsmarted me.
carb rebuild done. Choke still not functioning but that shouldnt matteR when up to temp. No discernable vacuum leaks. Timing is good. Both fuel filters replaced. Vacuum lines replaced. New PCV, new carb gaskets, etc. Makes about 18" of vacuum at idle...700-800 RPM.
i would shop for a new carb if I thought that would fix the truck but I dont feel like throwing good money at possibilities. Any experts in the phoenix area that could give me a hand? Not sure what else to troubleshoot.
carb rebuild done. Choke still not functioning but that shouldnt matteR when up to temp. No discernable vacuum leaks. Timing is good. Both fuel filters replaced. Vacuum lines replaced. New PCV, new carb gaskets, etc. Makes about 18" of vacuum at idle...700-800 RPM.
i would shop for a new carb if I thought that would fix the truck but I dont feel like throwing good money at possibilities. Any experts in the phoenix area that could give me a hand? Not sure what else to troubleshoot.
Postmaster
Joined: Mar 2011
Posts: 2,698
Likes: 7
From: Taxachusetts
Well....If you've tried these troubleshooters before I don't recall.
Try:
Low fuel pressure check. Should have around 7 psi.....check at various RPM ranges.
Carb mixture - settings done with a vacuum gauge to read the highest "Hg. You could have a lean stumble issue at WOT....basically, under load.........
.......and a "weak" ignition circuit not being able to produce enough juice to the plugs under load/WOT.
Check spark color, primary and secondary coil resistance, and for grins & chuckles, ohm out the plug wires.
Try:
Low fuel pressure check. Should have around 7 psi.....check at various RPM ranges.
Carb mixture - settings done with a vacuum gauge to read the highest "Hg. You could have a lean stumble issue at WOT....basically, under load.........
.......and a "weak" ignition circuit not being able to produce enough juice to the plugs under load/WOT.
Check spark color, primary and secondary coil resistance, and for grins & chuckles, ohm out the plug wires.
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
I am ready to shoot my truck at this point. There seems to be nothing I can do to address this throttle hesitation. Vacuum leaks addressed, new parts in the carb...accelerator pump diaphragm was backwards. It's right now and the truck is still stumbling when I try to accellerate like anyone but a grandpa. It will pull all the way to redline if I give it less than half throttle but if i give it more throttle than that it falls on its face, and then goes. I have a lot of $ in parts on order for the suspension thinking this shouldnt be hard to fix but it has outsmarted me.
carb rebuild done. Choke still not functioning but that shouldnt matteR when up to temp. No discernable vacuum leaks. Timing is good. Both fuel filters replaced. Vacuum lines replaced. New PCV, new carb gaskets, etc. Makes about 18" of vacuum at idle...700-800 RPM.
i would shop for a new carb if I thought that would fix the truck but I dont feel like throwing good money at possibilities. Any experts in the phoenix area that could give me a hand? Not sure what else to troubleshoot.
carb rebuild done. Choke still not functioning but that shouldnt matteR when up to temp. No discernable vacuum leaks. Timing is good. Both fuel filters replaced. Vacuum lines replaced. New PCV, new carb gaskets, etc. Makes about 18" of vacuum at idle...700-800 RPM.
i would shop for a new carb if I thought that would fix the truck but I dont feel like throwing good money at possibilities. Any experts in the phoenix area that could give me a hand? Not sure what else to troubleshoot.
This is by the sounds of it a fueling issue. Next step is to hook up a Vacuum gauge and run it in to the cab and see what the vacuum is doing when this happens. It may an issue with your combination and the Power Valve in the carb you are using either over or under fueling.
Also I do not recall is it standard or auto?
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Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
Carb mixture screws are only for Idle, this is likely a transition issue between the idle circuit and the main circuit.
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Elder User
Joined: Oct 2016
Posts: 712
Likes: 1
From: Mesa, AZ
I can check plugs. Have no way to check fuel pressure. Any suggestions on how I check this?
What should vacuum be at different RPMs? I'm at 18 or so at idle but the needle is jumping around a little. (+/- 1 or so)
Truck is a manual.
Power valve is new and came with the Napa rebuild kit. Had the same issue before the rebuild so don't think it's that, unless they're both bad or wrong.
What should vacuum be at different RPMs? I'm at 18 or so at idle but the needle is jumping around a little. (+/- 1 or so)
Truck is a manual.
Power valve is new and came with the Napa rebuild kit. Had the same issue before the rebuild so don't think it's that, unless they're both bad or wrong.
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Elder User
Joined: Oct 2016
Posts: 712
Likes: 1
From: Mesa, AZ
Too add, shouldn't there be enough fuel in the bowl to have good throttle response, at least for a moment, even if fuel pressure was low?
It'll pull enough fuel for 4000+ RPM (which is scary on a 351...lol), it just won't do it in a hurry.
It'll pull enough fuel for 4000+ RPM (which is scary on a 351...lol), it just won't do it in a hurry.
Tuned
Joined: Jun 2015
Posts: 375
Likes: 3
From: Southern OR
I just read through most of this thread, and it looks like you never got the vacuum advance working correctly??? You need to do that before anything else ...YOU NEED TO BE ABLE TO MOVE THAT ADVANCE ARM WITH YOUR MOUTH VACUUM. Adjust it accordingly with the allen wrench, I don't remember which way you turn it? I've had to back off the tension all the way on the last couple I worked on to get them to not stumble off idle, and or rolling start.
The last 351m dizzy I worked on had a sticky vacuum advance, talk about goofy timing, it would idle high at times, sometimes not?, it would have a flat spot, and sometimes it would hard hot start...ALL BECAUSE OF THE ADVANCE NOT WORKING PROPERLY.
After you get the dizzy working properly, move on to the carb/fuel adjustments. This is my order of trouble shooting anyway...I hope it helps
The last 351m dizzy I worked on had a sticky vacuum advance, talk about goofy timing, it would idle high at times, sometimes not?, it would have a flat spot, and sometimes it would hard hot start...ALL BECAUSE OF THE ADVANCE NOT WORKING PROPERLY.
After you get the dizzy working properly, move on to the carb/fuel adjustments. This is my order of trouble shooting anyway...I hope it helps
Thread Starter
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Elder User
Joined: Oct 2016
Posts: 712
Likes: 1
From: Mesa, AZ
I just read through most of this thread, and it looks like you never got the vacuum advance working correctly??? You need to do that before anything else ...YOU NEED TO BE ABLE TO MOVE THAT ADVANCE ARM WITH YOUR MOUTH VACUUM. Adjust it accordingly with the allen wrench, I don't remember which way you turn it? I've had to back off the tension all the way on the last couple I worked on to get them to not stumble off idle, and or rolling start.
The last 351m dizzy I worked on had a sticky vacuum advance, talk about goofy timing, it would idle high at times, sometimes not?, it would have a flat spot, and sometimes it would hard hot start...ALL BECAUSE OF THE ADVANCE NOT WORKING PROPERLY.
After you get the dizzy working properly, move on to the carb/fuel adjustments. This is my order of trouble shooting anyway...I hope it helps
The last 351m dizzy I worked on had a sticky vacuum advance, talk about goofy timing, it would idle high at times, sometimes not?, it would have a flat spot, and sometimes it would hard hot start...ALL BECAUSE OF THE ADVANCE NOT WORKING PROPERLY.
After you get the dizzy working properly, move on to the carb/fuel adjustments. This is my order of trouble shooting anyway...I hope it helps
I wasn't convinced I had an issue with the distributor. I did buy a new one and applied suction to it through the vac advance and nothing moved on it either. Bad distributor or just not enough suction?
I have to pull the whole dist to get to the vac advance can because of the damned compressor mounting bracket for the AC. I might see if I can find an inexpensive vacuum pump to test it that way.
I will also go back to another issue....timing. Where my pointer is, I'm showing damn near 20 degrees of advance at idle which is way too much, but I tend to not believe the pointer since there's no dieseling, no pinging, and the idle is good. That leaves me unable to trust where my timing is, and concerns me about pulling the distributor. Am guessing that timing is closer to 10-12 degrees BTDC, but I have no way of confirming. Yes, the vac advance was disconnected when I checked.
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Elder User
Joined: Oct 2016
Posts: 712
Likes: 1
From: Mesa, AZ
Ok, can rule out vacuum advance. I picked up a vac pump on the way home today and was able to sse the distributor advance when vacuum was applied. Fuel pressure or internal carb issue...down to that I guess. Tips on checking the fuel pressure? Just dont know how to do that.
Postmaster
Joined: Mar 2011
Posts: 2,698
Likes: 7
From: Taxachusetts
If one has the carb's mixture tuned using manifold vacuum, 9.9 times out of 10 the curb idle will have to be adjusted to a lower RPM. This allows the throttle plates to be closed more....and the transition slots won't be open as much....and won't be engaging the main circuit. With the mixture then set right, a smoother transition from idle to off idle/acceleration (pump) will occur.
Fuel pressure check: You'll have to buy a fuel pressure gauge - either an in-line one that can stay or a "stand alone" one hooked up with a "T" in line. Look for > 6 psi.
Timing: You could make a piston stop from an old spark plug or buy one on line. To use - pull the plugs, screw in the piston stop after ascertaining #1 cylinder is just coming up on the compression stroke. Turn the engine CW until #1 piston just touches the stop. Make a mark on the balancer at the pointer. Turn the engine CCW until the piston just touches the stop. Make a mark on the balancer again. Take the distance between the two marks and divide by two, and make a mark. That's TDC. Now you can see where your timing is at.