Strange fuel surging on highway?

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Topic author
ericthered
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Joined: Sun Jan 26, 2020 11:03 pm

Strange fuel surging on highway?

Post by ericthered »

Hello,
Strange issue when im on the highway driving for about 10 to 15 min, the wagoner looses power and starts to surge a bit. When I say loosing power it goes from 60 mph @ 2700 rpm to 25mph and even with the foot to the floor just stumbles and has no power. If I pump the gas it will get a little better enough to keep the truck going but no power at all to regain speed. As soon as I get off the freeway and pull over I can floor the gas and it regains power and revs. Then on the side streets it has no issues at all?? Never dies or stumbles.

Jeep is 1966 with 350 chevy with a new Edelbrock 500cfm. Filter next to carb is clean, and car is not hot under hood to cause vapor lock? Gas cap is normal 1970 model twist and it feels like its sealed. In the summer I had issues after I put gas in the tank that when heated from sitting in the sun it would push gas out the gas filler?
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fulsizjeep
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Re: Strange fuel surging on highway?

Post by fulsizjeep »

This sounds like vapor lock to me but it's possible the fuel pump is not producing the volume you need. What kind of fuel pump do you have and where is it located?
Flint Boardman
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will e
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Re: Strange fuel surging on highway?

Post by will e »

Welcome to the board! Post up and introduce yourself and also post some pics!

It sure 'sounds' like vapor lock. If you can, put a fuel pressure gauge close to the carb. If you can do an 'in cab' one even better.

Does your jeep have a 'return' line from the fuel filter? I don't recall if the older jeeps had one or not.
81 Waggy 'WILL E' Retired
82 Cherokee WT - SOA/SF/high steer/Alcan springs/agr box/Borgeson steering shaft/AMC 401/performer/holley TA/HEI/BeCool/727/ALTAS (2.0/2.72/5.44)/D60 Snofighter(Yukon Zip,hubs,stubs,4.56)/14 Bolt (FF,BF shave, Discs, ARB,Artec Truss)/MTR 37X12.5/Corbeau XRS Baja & 5 point retractable harness/Hella Aux lights/tuffy console/killer32 sliders/Evil Twin bumpers, rack and roll cage/WARN 8000/TT Fabworks steering brace/dual batts/custom TC skid plate/ARB fridge

Topic author
ericthered
Posts: 13
Joined: Sun Jan 26, 2020 11:03 pm

Re: Strange fuel surging on highway?

Post by ericthered »

Not sure the fuel pump, but its a regular mech on the motor. not an electric. I'll take a look if I can see any markings.

The fuel filter on the jeep is the plastic clear kind next to the carb, so no return line from that.

What I can figure is just driving around town (stop and go) it does not have any issues and never starves and the motor would be hotter just idling around. At highway speeds the air alone would keep the bay cooler?

Is there any kind of gas pressure issue from the tank that could cause this? Always happens around 10 to 15 on the highway, wondering if its building pressure or has a vent issue?

will e
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Re: Strange fuel surging on highway?

Post by will e »

I have found most often that I have issues with vapor lock on the highway more than on the street. I think on the street the carb bowls have a bit more chance to fill up since you use a lot less gas at idle. Also, you tend to be driving slower. But I admit, when I had vapor lock issues, it would happen on really hot days while driving around town.

If the tank get pressurized, it would probably vapor lock.
81 Waggy 'WILL E' Retired
82 Cherokee WT - SOA/SF/high steer/Alcan springs/agr box/Borgeson steering shaft/AMC 401/performer/holley TA/HEI/BeCool/727/ALTAS (2.0/2.72/5.44)/D60 Snofighter(Yukon Zip,hubs,stubs,4.56)/14 Bolt (FF,BF shave, Discs, ARB,Artec Truss)/MTR 37X12.5/Corbeau XRS Baja & 5 point retractable harness/Hella Aux lights/tuffy console/killer32 sliders/Evil Twin bumpers, rack and roll cage/WARN 8000/TT Fabworks steering brace/dual batts/custom TC skid plate/ARB fridge

MReese Wagoneer
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Re: Strange fuel surging on highway?

Post by MReese Wagoneer »

I believe a fuel pressure issue, whether vapor lock or the pump cant keep up or the "New" carb
put an in line fuel pressure gauge , but you cant see it while driving :( see if you can remote it somewhere so you can monitor it, unless a friend wants to ride under the hood while you go down the highway
:fsj:
New 83 Wagoneer Brougham
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will e
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Re: Strange fuel surging on highway?

Post by will e »

MReese Wagoneer wrote: Mon Jan 27, 2020 11:40 am I believe a fuel pressure issue, whether vapor lock or the pump cant keep up or the "New" carb
put an in line fuel pressure gauge , but you cant see it while driving :( see if you can remote it somewhere so you can monitor it, unless a friend wants to ride under the hood while you go down the highway
Or a well placed 'go pro'.
81 Waggy 'WILL E' Retired
82 Cherokee WT - SOA/SF/high steer/Alcan springs/agr box/Borgeson steering shaft/AMC 401/performer/holley TA/HEI/BeCool/727/ALTAS (2.0/2.72/5.44)/D60 Snofighter(Yukon Zip,hubs,stubs,4.56)/14 Bolt (FF,BF shave, Discs, ARB,Artec Truss)/MTR 37X12.5/Corbeau XRS Baja & 5 point retractable harness/Hella Aux lights/tuffy console/killer32 sliders/Evil Twin bumpers, rack and roll cage/WARN 8000/TT Fabworks steering brace/dual batts/custom TC skid plate/ARB fridge

RamJetFSJ
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Re: Strange fuel surging on highway?

Post by RamJetFSJ »

Sounds like pump not keeping up to me. Or fuel lines/pickup clogged. Fuel flow is as important as pressure.
80 Wag in 73 attire, Ram Jet 350 power

letank
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Re: Strange fuel surging on highway?

Post by letank »

time to measure fuel pressure, but also float height vs. to specs. I like the gopro idea, or you can remove the washer nozzle and install a hose thru it and secure a fuel pressure gauge on the cowl, or drill a hole... one time I lost patience and drilled a hole in the hood...

Image

or using the old washer nozzle holes on later models with an intermediate copper line, it clears the hood, that was for a vacuum check, and the previous hole was nicely patched...

Image
Michel
74 wag (349 Kmiles... parked, next step is a rust free body)
85 Gwag (229 Kmiles... the running test lab)

PossumJr
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Re: Strange fuel surging on highway?

Post by PossumJr »

I used to experience the same issue. Would idle and cruise at 55 just fine, but running at freeway speeds for more than a few minutes would result in surging. Replaced the old mechanical fuel pump and it went away. Combination of heat and a weak pump is what I assume would do it and the fuel flow wasn't able to keep up for what was being used at those speeds.
1979 J10, 360/QT

will e
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Re: Strange fuel surging on highway?

Post by will e »

letank wrote: Mon Jan 27, 2020 2:26 pm one time I lost patience and drilled a hole in the hood...
I know you and this does not surprise me. ;)

Hey, whatever works!
81 Waggy 'WILL E' Retired
82 Cherokee WT - SOA/SF/high steer/Alcan springs/agr box/Borgeson steering shaft/AMC 401/performer/holley TA/HEI/BeCool/727/ALTAS (2.0/2.72/5.44)/D60 Snofighter(Yukon Zip,hubs,stubs,4.56)/14 Bolt (FF,BF shave, Discs, ARB,Artec Truss)/MTR 37X12.5/Corbeau XRS Baja & 5 point retractable harness/Hella Aux lights/tuffy console/killer32 sliders/Evil Twin bumpers, rack and roll cage/WARN 8000/TT Fabworks steering brace/dual batts/custom TC skid plate/ARB fridge

bigun
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Re: Strange fuel surging on highway?

Post by bigun »

Last time I went to Tucson in my 91 D-150 which has an in tank fuel pump I had trouble with surging, scared me that truck had always been old faithful called BlackBart and he theorized that it was the alcohol added to fuel was causing a partial vapor lock going up hills. I had the same problem with The Great Pumpkin my class C RV. When I came home I left after dark towed the D-150 behind the motor home temps were probably in the 80s as opposed to the 90s the 460 never skipped a beat

KJ Ryu
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Re: Strange fuel surging on highway?

Post by KJ Ryu »

Sniff the dipstick. If it smells at all like gas, change the fuel pump and oil/filter.
Ron

2005 KJ, Hit-n-Run, 2am 6-17-2012, Totaled. :mad:
1977 SJ J10, 4v360, T18, D20, 37x14s, SOA & SF on tons, still ugly.
1978 SJ Wagoneer, 4v360, QT, 33x12.5s, lift by Sawzall :-bd NOT Running :(
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Topic author
ericthered
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Joined: Sun Jan 26, 2020 11:03 pm

Re: Strange fuel surging on highway?

Post by ericthered »

Ok So I'm still in process on this, taking a bit longer then expected. Thanks for the comments and suggestions!

So far I think it's either a vapor lock issue, or a fuel pump not making enough fuel pressure when in demand. So I'm moving the filter further away from the engine, it was near the carb above the valve cover but not laying in it. I'm moving it.

The second thing is I bought a new Edelbrock 1721 fuel pump, to replace the older Mech pump. Figured since I don't know how old the last pump is it could not hurt. When I pulled it I noticed there is more play in the lever and spring compared to the new pump. Maybe this is just worn out? I've never had to replace one before so I'm not sure.

Replacing the old pump with an. Edelbrock to match up to the Edelbrock 500cfm carb. Figured best to match and the pump does not need a regulator and does a max of 6 pounds. Hoping that the bog was from lack of fuel to the bigger carb then what was there before.

Hope to get it back together in the next few days, if anyone has more comments please fire away!

will e
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Re: Strange fuel surging on highway?

Post by will e »

If you can spend the money get a fuel gauge for the cab with a remote sensor. It will help diagnose your current issue and, in the future, if you have problems it will tell you almost immediately if it is a fuel or ignition problem.

My electric fuel pump 'died'. It was 'running' and making noise but not providing any pressure. Because I had the gauge in the cab I knew immediately what the problem was and fixed it on the side of the road in about 30 minutes. (I carry a spare electric pump).
81 Waggy 'WILL E' Retired
82 Cherokee WT - SOA/SF/high steer/Alcan springs/agr box/Borgeson steering shaft/AMC 401/performer/holley TA/HEI/BeCool/727/ALTAS (2.0/2.72/5.44)/D60 Snofighter(Yukon Zip,hubs,stubs,4.56)/14 Bolt (FF,BF shave, Discs, ARB,Artec Truss)/MTR 37X12.5/Corbeau XRS Baja & 5 point retractable harness/Hella Aux lights/tuffy console/killer32 sliders/Evil Twin bumpers, rack and roll cage/WARN 8000/TT Fabworks steering brace/dual batts/custom TC skid plate/ARB fridge

letank
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Re: Strange fuel surging on highway?

Post by letank »

will e wrote: Sat Feb 01, 2020 7:31 am If you can spend the money get a fuel gauge for the cab with a remote sensor. It will help diagnose your current issue and, in the future, if you have problems it will tell you almost immediately if it is a fuel or ignition problem.
Excellent Idea, can you give us some parts numbers and vendor...

I have been battling one issue... which ended being 3 bugs, none related to fuel pressure, but I am sure that it will be my next bug. I do carry a spare pump too, but it is easier to see what is happening. In fact my fuel pump failure was a slow failure... bogging at freeway speed, then hard to go uphill, so I connected the fuel pressure, and I was a barely 2 psi... at least it gives you the time to find the best repair spot, or underpass when it is pouring or any safe location:

Image
Michel
74 wag (349 Kmiles... parked, next step is a rust free body)
85 Gwag (229 Kmiles... the running test lab)

will e
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Re: Strange fuel surging on highway?

Post by will e »

That's a great picture Michel!


I use this one:
https://www.autometer.com/2-fuel-press- ... obalt.html

It's pricey, I am sure they can be found for less. Although any electric gauge with a remote sensor is going to run close to two bills.
81 Waggy 'WILL E' Retired
82 Cherokee WT - SOA/SF/high steer/Alcan springs/agr box/Borgeson steering shaft/AMC 401/performer/holley TA/HEI/BeCool/727/ALTAS (2.0/2.72/5.44)/D60 Snofighter(Yukon Zip,hubs,stubs,4.56)/14 Bolt (FF,BF shave, Discs, ARB,Artec Truss)/MTR 37X12.5/Corbeau XRS Baja & 5 point retractable harness/Hella Aux lights/tuffy console/killer32 sliders/Evil Twin bumpers, rack and roll cage/WARN 8000/TT Fabworks steering brace/dual batts/custom TC skid plate/ARB fridge
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ghcoe
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Re: Strange fuel surging on highway?

Post by ghcoe »

I went through a vapor lock type issue when I got my Jeep back on the road a few years ago. Would work fine until it got heat soaked. Never had a problem when I had it running before.

In searching for a solution this is what I found.

-First thing I though was the fuel pump. Changed fuel pump and filter at this point. Helped but still had issues.
-Second thing I found was the short rubber hoses going from the tank to the steel lines were weathered and cracked. Figured this out by trying to track down a raw fuel smell when parked. Fuel was actually leaking out through the rubber and onto the top of the tank. It would not leak when running due to the pump suction, but once shut off would slowly leak out onto the top of the tank. Just enough that it was hard to see when I looked for where the smell was coming from. Took a bit to figure this out. I figured that was also the issue to the fuel starvation since the pump was probably sucking air through the cracks. Although it made a big difference, especially at start up since it did not have to reprime the lines, I still had a vapor lock issue.

At this point I was getting pretty frustrated with this issue.

-Third thing I thought was the issue, since I did not have the issue before it was parked, was the fuel pick up sock in the tank. Took the tank out and found no major issue. Tank looked fine, sock looked fine, but I removed it completely just to make sure. Went ahead and flushed tank. No change at all

Removing the tank was a big pain and it wound up being a big zero on performance. Not happy!

-Fourth thing I though, by reading forum posts is that the fuel pumps are made in China now and everyone says they are junk. Hit and miss if you get a good one. Now I really don't believe that myself, But...……….. at this point I am grabbing at straws. I replaced the pump again with a different pump brand. Well no change in performance.

-Just a note for reference. After I removed the sock in the tank I installed a clear fuel filter before the pump to compensate for no tank sock. On my way home from a off road trip the Jeep began to fuel starve bad. Maintained road speed slowly decreased to where I could barely maintain 10 mph when I got home. I thought the pump was going out. It turned out the clear filter, which looked fine, had clogged up. I had tapped it on the driveway just to see if anything would drop out of the element and found what looked to be clear sand fall out of it. Not sure where it would come from. Though maybe from the pump, but who knows. I carried spare filters with me and changed them out about 3 times before this condition went away. Usually the issue happened just after a off road trip. I figured the rough roads sloshed the fuel enough to suspend this contaminate in the fuel and then through the lines. Just so you know the filters looked fine when inspecting them, but once tapped to knock out the particles from the element you can clearly see clear sandy deposits.

-Fifth thing I tried was putting 3/4" heater hose around the fuel lines to try and keep them cool. At this point it was vapor locking on 90+ hot days and only once it was driven on the freeway for over 10 miles (heat soaking, I thought).

-Sixth thing I tried was installing a Holley Red electric fuel pump from online recommendations to cure vapor lock (I don't recommend Holley Red), but fuel starvation problem fixed!

-Reading a lot of post online I finally found some great information on vapor lock. Turns out there is a lot of misconceptions cure.
1. Vapor lock occurs in the lines before the pump, not behind the pump. Metal lines get hot and turns liquid fuel to vapor. Mechanical and electric pumps mounted towards the front of the vehicle can both have vapor lock issues. Electric pumps mounted towards the back of the vehicle are not as prone to vapor lock since they pressurize the fuel in the line where heat occurs. Higher line pressure cures lower boiling point issues.
2. This is the one that made sense to me. Fuel formulas today have a lower boiling point since modern cars are fuel injected. This is why even if everything is working fine in a older vehicle you may still have issues with vapor lock. Of course this does depend on how the original fuel system was set up. With the Jeep the fuel lines do run close to the exhaust manifold.

Conclusion-Yes it was a frustrating task to find out the issue. In actuality all these things or just one of these things could be the problem. The fuel formula information I read really made a lot of sense to me. I was chasing my tail, in a way, because I had no issues at all when the Jeep was on the road before. Thinking that I could achieve that reliability again with the stock type pump was what I was after. Once I realized the fuel formula difference it made sense that I had to look at this entirely in a different matter. The electric pump was the last thing I did to the fuel system outside of replacing the steel lines. It solved the problem.

Things to note If I was to do this again knowing what I know now.
-First thing I would do is check the rubber fuel lines going from the tank to the steel fuel lines.
-Second install a electric fuel pump. I found these pumps to work great https://www.oreillyauto.com/detail/b/pr ... pump&pos=2 . I chose these pumps since they are available at O'reilly's auto parts and carry a lifetime warranty. They are sold under different brand names as well such as Carter, which I believe is the original manufacture for this style of pump. They run fuel through the motor to keep it cool and they are pretty quiet. I run two, one for each tank, and have been running one over 2 years and the other a little over a year with no issues at all. My experience with the Holley Red, which was recommended, is dismal. Started to leak out the motor in under a year and was very noisy. Not to mention expensive.
-Since these repairs and installation of electric fuel pumps I have had absolutely no fuel starvation issues at all. I used this Jeep as a daily driver to work and back 50 miles round trip as well as off road adventures. Many trips requiring high speed, long distance freeway travel. Often pulling my tear drop trailer on these trips. You can check them out here https://www.youtube.com/channel/UCYuRx2 ... wVwZJ5oztg? . Yes it is good to have dependability back. See you on the trails, George.
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Topic author
ericthered
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Joined: Sun Jan 26, 2020 11:03 pm

Re: Strange fuel surging on highway?

Post by ericthered »

Thanks for posting such a detailed background of your story of solving the fuel issue. Took lots of mental notes off this post.

So far I've got to get the fuel pump back on, should be this week. I'll check over all the rubber hose, so not to get air in the line and also don't need that to break and catch fire. Did you have any clogging in the vent hose? Guy at NAPA said some words about that yesterday.

Was trying not to run an electric due to the fact in the past I've had issues with them. But if I have to then I have to. On the model you suggested I'm only running one tank on the car so I assume you mounted yours on the rail closest to the outlet on the tank. When you said to keep it cool you run fuel through it...don't understand what you may be saying there can you expand the detail on that.

Again thanks for the posts.

will e
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Re: Strange fuel surging on highway?

Post by will e »

I know one sure way to verify if it is fuel lock.

Take it for a drive with about 1/4 or so tank of gas. Half a tank would be fine but the less gas the better.

Once it is consistently acting up, stop and fill the gas tank. Start driving again. If the problem clears up in a mile or so you were having vapor lock or fuel boiling issues. The symptoms go away when you fill the tank because the new fuel is very cool from being in the underground tanks.
81 Waggy 'WILL E' Retired
82 Cherokee WT - SOA/SF/high steer/Alcan springs/agr box/Borgeson steering shaft/AMC 401/performer/holley TA/HEI/BeCool/727/ALTAS (2.0/2.72/5.44)/D60 Snofighter(Yukon Zip,hubs,stubs,4.56)/14 Bolt (FF,BF shave, Discs, ARB,Artec Truss)/MTR 37X12.5/Corbeau XRS Baja & 5 point retractable harness/Hella Aux lights/tuffy console/killer32 sliders/Evil Twin bumpers, rack and roll cage/WARN 8000/TT Fabworks steering brace/dual batts/custom TC skid plate/ARB fridge
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