1971 deuce uneven power performance

[Mud Hugger]

To start with I will say I love my duece it's my utility truck. I have added the naps muffler to quiet the beast, I have added a scissor hoist and rear hitch/reciever plate. It's running supper single 395s which was a incredible upgrade for offroad. Even before I put the large treads on it it seemed to be a different truck every time I would drive it. Some times it would struggle to get over 2000rpms and would be a mule to get even up to 50mph. Then the next time out I could shift at 17-1800rpms and she would cruise ad get up to 55-60 in a short time. (respectfully speaking) I have change fuel filters twice with no noticeable change after, I've changed air filter, and still doesn't seem to help the temperamental beast. I have not modded fuel rate or anything on truck. If I want power I'd swap in a cummins but I like it as it is and the originality of te truck. I haul snow,firewood, some gravel, rocks and pull out trucks at local Boggs. I love it just want it to be constant performance. Any help please!!!

 

[HanksDeuce]

Do you have any aftermarket gauges on the truck? A boost gauge and pyrometer (exhaust gas temperature) would help to determine fuel rate.

For reference, my M35A2 originally ran 4-5psi of boost. I turned the fuel screw up to 14psi of boost, and she turned into a totally different truck. And the exhaust never got above 1050F.

 

[Mud Hugger]

Do you have any aftermarket gauges on the truck? A boost gauge and pyrometer (exhaust gas temperature) would help to determine fuel rate.

For reference, my M35A2 originally ran 4-5psi of boost. I turned the fuel screw up to 14psi of boost, and she turned into a totally different truck. And the exhaust never got above 1050F.

Ya I have them just haven't put them in. Its the plan to get them in. Just wondering why the rig is goofy if the pump is weak or what. Sonedays she will just get up and go get right up to 60mph with ease. Other days it's a struggle to get up to 50mph. I am planning on guage a installed and testing.
Is 14psi max for these multifuels? I'm all about increasing power but I dont want to kill it. I run a lot of WMO, old filtered hydraulic oil and little gas when i prep the boat every spring. I try to go 50/50 with good diesel.

 

[Jeepsinker]

I bet your in tank pump is working intermittently. Mine had the same symptoms. It is surprising how much power you lose when the lift pump doesn't work.

 

[Mud Hugger]

And good way to test Lift pump or psi from lift pump? Does it pump all the time with power switch on? Now that you mentioned lift pump My gen 1 cummins did this. It would idle ok but hit the pedal and in a few seconds she would putter out.

 

[Mud Hugger]

Oh and talk about a guttless wonder when she's hepped 2ft over cab with firewood. Wow...I think I can push it faster!!

 

[Jeepsinker]

You can plumb in a small pressure gauge with 1/8" fitting. There is a square metal block on top of the fuel pump that the fuel supply line runs out of. On the side facing out toward you is a plug( looks like a bolt run halfway in). Take that plug out and install the gauge there. You should have a constant 4-7 psi. Only problem is that you may have pressure sitting there idling, but you run down the road and hit a bump and the pump cuts out. Can't see the gauge while you are driving.

 

[Mud Hugger]

You can plumb in a small pressure gauge with 1/8" fitting. There is a square metal block on top of the fuel pump that the fuel supply line runs out of. On the side facing out toward you is a plug( looks like a bolt run halfway in). Take that plug out and install the gauge there. You should have a constant 4-7 psi. Only problem is that you may have pressure sitting there idling, but you run down the road and hit a bump and the pump cuts out. Can't see the gauge while you are driving.

I Can just use oil psi tubing an run it up in cab. I will get her rigged up an try it out. If it cuts in and out can it just be a wiring issue or more likely the pump is bad. Does the rig have to be run with that in tank pump or can an inline electric pump replace it.

 

[roscoe]

I saw C&C equipment had a replacement inline pump when browsing the site for fuel related parts.

 

[skinnyR1]

You can plumb in a small pressure gauge with 1/8" fitting. There is a square metal block on top of the fuel pump that the fuel supply line runs out of. On the side facing out toward you is a plug( looks like a bolt run halfway in). Take that plug out and install the gauge there. You should have a constant 4-7 psi. Only problem is that you may have pressure sitting there idling, but you run down the road and hit a bump and the pump cuts out. Can't see the gauge while you are driving.

Thats what I did too.

 

[machinist75]

There are nice in tank pumps on epay for $50. Not original but fit just rite and work better.

 

[Mud Hugger]

When does the in tank pump get power? When power switch is on your when the truck is running?

 

[welldigger]

When the main power switch is on.

 

[Mud Hugger]

Well checked for power. We have 25.4v at plug. So im think pump must be out cuse I can't hear or fell anything on the head. I'm picking up a JIC to 1/8 pipe fitting tomorrow and hook my psi gauge into it and make sure. But if it's dead I'm ordering a inline pump. What you guys think? A inline pump with 5-10 psi be good? Or should I just get a standard in tank pump?

 

[Mud Hugger]

There are nice in tank pumps on epay for $50. Not original but fit just rite and work better.

I just looked at these 50$ pumps. Those are some nice looking replacements to the old unit. Im going to have to think about this. This will keep it more stock than an inline. Thanks for the idea

 

[welldigger]

I just looked at these 50$ pumps. Those are some nice looking replacements to the old unit. Im going to have to think about this. This will keep it more stock than an inline. Thanks for the idea

They are cheaper and easier to deal with than an in line pump also.

 

[porkysplace]

Well checked for power. We have 25.4v at plug. So im think pump must be out cuse I can't hear or fell anything on the head. I'm picking up a JIC to 1/8 pipe fitting tomorrow and hook my psi gauge into it and make sure. But if it's dead I'm ordering a inline pump. What you guys think? A inline pump with 5-10 psi be good? Or should I just get a standard in tank pump?

Is the plug you checked before or after the fuse on the pump . You may want to verify the fuse is good before replacing the pump.

 

[Mud Hugger]

I pulled the plug right off sending unit top. Is the fuse under the cover or in tank? Enlighten me where it's located.

 

[welldigger]

Yes. The cover the plug hooks to.

You need a 7 amp slow blow fuse.

 

[Mud Hugger]

I do have power after fuse going down into tank.