No power at idle

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WillWagner

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Here's something I have not seen that it has been checked. The FSOV. If it has a broken link or not pulling up the correct distance....not enough OR too much.... The rack in the pump will not be able to go to full fuel, it will orient the dump slot in the wrong position and shunt the fuel away from the delivery valves. What is it idling at?
 

fpchief

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Here's something I have not seen that it has been checked. The FSOV. If it has a broken link or not pulling up the correct distance....not enough OR too much.... The rack in the pump will not be able to go to full fuel, it will orient the dump slot in the wrong position and shunt the fuel away from the delivery valves. What is it idling at?
I will verify and post. I know it usually idles a little higher than what it is set at due to sticky throttle. Can put my boot under pedal and lift it a little to make it idle down.
 

glcaines

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Reverse is roughly 2-1/2 times lower gear ratio.
I understand that. What happens if low range is selected. I'm wondering if the transmission is not actually in 1st gear. I had a truck once that, when cold, the transmission hung up in third gear and the truck would barely move from stopped. I determined the problem by jacking up the rear end and found the wheels spinning much faster than if in 1st. With that problem, I also first thought I had a fuel problem.
 

74M35A2

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I understand that. What happens if low range is selected. I'm wondering if the transmission is not actually in 1st gear. I had a truck once that, when cold, the transmission hung up in third gear and the truck would barely move from stopped. I determined the problem by jacking up the rear end and found the wheels spinning much faster than if in 1st. With that problem, I also first thought I had a fuel problem.
Another good path. Anything is possible. Easy to check and rule out.
 

fpchief

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Update on low/no power when leaving from idle....as I had said, the aneroid and fuel screw mostly fixed it however now it seems "sometimes"...maybe half the time when leaving from idle it has no power...then other half of time if gets rolling raly good.

I think it is a boost issue....aneroid turned all the way toward motor. But if not being supplied boost, it does no good...right?
 

smoke

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Right to a point. Does it still roll a lot of smoke when it does not roll out good? If it does than you know you have the main fuel turn up enough and it boost problem or ?. If it doesn't than you may still have a fuel problem or something. Or need to turn main fuel up more. Think of the aneroid as a accelator pump on carb when you punch the gas it give it that extra gas until jets catch up to demand need. Hope that helps
 

fpchief

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Right to a point. Does it still roll a lot of smoke when it does not roll out good? If it does than you know you have the main fuel turn up enough and it boost problem or ?. If it doesn't than you may still have a fuel problem or something. Or need to turn main fuel up more. Think of the aneroid as a accelator pump on carb when you punch the gas it give it that extra gas until jets catch up to demand need. Hope that helps
Nope, no nothing when it wont go. But the times that it does go, it does roll alot. That analogy does help!!!
 

74M35A2

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Kind of, but opposite actually. It holds back fuel until boost pressure comes up to prevent black smoke out the exhaust. It is just a diaphragm against spring pressure, and a lever down to the main fuel rack. Boost pressure in the top reference line pushes on the diaphragm and against the spring pressure (star wheel adjustable), which then allows further travel of the fuel rack below it.
 

smoke

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I know this is for a p pump but if you look up BD-power afc spring kit for 94-98 dodge cummins click on instruction it explain how afc works. I don't know if you could use one of the spring to upgrade mw pump either. The other thing I don't know is if the fuel rack can be slid forward in the mw pump in cause yours is bind up on take off. I'm still wondering if it a fuel starvation problem. You can also look up on youtube, MW pump. There's a member here (nevrenufhp) that does show the adjustments on this pump on dt 360. He said something about you can adjust spring tension on afc beside the star wheel. I forgot to ask do you have a egt gauge that would help diagnose problem? Sorry for rambling..
 

WillWagner

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P and MW are different animals, give me the number on the pump and i'll see if the parts are interchangeable. It is not uncommon to have an intermittant issue inside the pump. If you have checked all of the pressures, FSOV, restriction, air in fuel and throttle travel, wastegate and plumbing aand AFC plumbing only 2 things are at fault. Injectors, but they usually have issues all of the time when there are problems like plugging, or a fuel pump, usually in the governor end and a worn linkage broken spring but sometimes it is in the right place at the right time and works/not works. Turbos on the older engines are 99% reliable and do not work sometimes and sometimes not.
 

fpchief

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P and MW are different animals, give me the number on the pump and i'll see if the parts are interchangeable. It is not uncommon to have an intermittant issue inside the pump. If you have checked all of the pressures, FSOV, restriction, air in fuel and throttle travel, wastegate and plumbing aand AFC plumbing only 2 things are at fault. Injectors, but they usually have issues all of the time when there are problems like plugging, or a fuel pump, usually in the governor end and a worn linkage broken spring but sometimes it is in the right place at the right time and works/not works. Turbos on the older engines are 99% reliable and do not work sometimes and sometimes not.
Thanks, I will get it this evening.
 

Jbulach

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Unless you have a fuel pressure gauge mounted in the cab, and verify no low pressure issues when the problem occurs. I would throw a cheap $25 lift pump at it, wouldn’t hurt to have a spare laying around anyhow... I had a similar problem, and it was the lift pump.
 

fpchief

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Unless you have a fuel pressure gauge mounted in the cab, and verify no low pressure issues when the problem occurs. I would throw a cheap $25 lift pump at it, wouldn’t hurt to have a spare laying around anyhow... I had a similar problem, and it was the lift pump.
It can be intermittent with lift pump?
 

WillWagner

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Not usually, unless there is a restriction that is intermittent, like something sucking up on the pick up. Same with overflow valve. That's why I said if you have checked everything....the stuff in a prior post.... 98% of the time it is one of two, pump or injectors. IF this came into the shop and all of the checks came out where they needed to be, I would give you an option. Either pump or injectors, but like I said, injectors usually do not have intermittent issues, they pop off where they should or have a low pop pressure, causing smoke/knock. If injectors like the pintle style in the C are plugged, it is usually from something downstream, like a pump failure or rust. Most of the time, given the issue, pumps are $, injectors aint, so we would put a set in and give it a whirl. I have put injectors in things, passed it on the dyno and road tested, worked great, customer took it but was back in a few days to do the pump.

Checks. Full throttle, FSOV pull in/hold in, fuel pressure, restriction from the tank and pressure drop across the pressure filters, AFC line plumbing, including the waste gate line and capsule...don't remember if these have a WG.

Fuel psi should be 25-35 psi, restriction, 4 in vacuum, drop across filter....I wanna say 4 psi, it has been a bit. To test the WG, remove the line at the head, put regulated shop air to it and slowly increase the pressure, rod starts to move about 20 psi, use soap/water on the capsule where the rod goes into it, no bubbles, no leak. Bubbles, leaking.
 

fpchief

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P and MW are different animals, give me the number on the pump and i'll see if the parts are interchangeable. It is not uncommon to have an intermittant issue inside the pump. If you have checked all of the pressures, FSOV, restriction, air in fuel and throttle travel, wastegate and plumbing aand AFC plumbing only 2 things are at fault. Injectors, but they usually have issues all of the time when there are problems like plugging, or a fuel pump, usually in the governor end and a worn linkage broken spring but sometimes it is in the right place at the right time and works/not works. Turbos on the older engines are 99% reliable and do not work sometimes and sometimes not.
Here are my pump numbers!
 

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fpchief

Active member
Steel Soldiers Supporter
781
64
28
Location
Bay Minette, Al.
I know this is for a p pump but if you look up BD-power afc spring kit for 94-98 dodge cummins click on instruction it explain how afc works. I don't know if you could use one of the spring to upgrade mw pump either. The other thing I don't know is if the fuel rack can be slid forward in the mw pump in cause yours is bind up on take off. I'm still wondering if it a fuel starvation problem. You can also look up on youtube, MW pump. There's a member here (nevrenufhp) that does show the adjustments on this pump on dt 360. He said something about you can adjust spring tension on afc beside the star wheel. I forgot to ask do you have a egt gauge that would help diagnose problem? Sorry for rambling..
I do not have an EGT, I need to get one. you mentioned in an earlier post the main fuel adjustment. You are talking about the one on the very end of the pump facing the cab? I did turn the one under the cap on top of the pump...just some.

Driving today, problem still there, great until I have to stop. Going to turn screw on top of pump more and also mess with the one on back of pump I think. I need to see if I have any boost on the boost line going to the pump.
 

smoke

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oxford,pa
Hope this works.
nevrenufhp
Registered

Joined Jul 14, 2005
310 Posts

#6 Aug 9, 2016
When I go do a pump, I start with the nuts on the back, and back out the screw on top a few turns just to wake it up a bit.
That screw on top is essentially the adjustment for starting and low rpm. Back it out, and the cut off point goes to a higher rpm. Gives a good punch off the line. If you go too far it will smoke real bad when you take off. Which leads to the star wheel. This is the last one to do. More of a fine tuning after you do the other 2 adjustments.
None of it is a set science, since pumps and injectors are different.


my Low buck diesel fuel rate site: http://www.freewebs.com/nevrenufhp/index.htm
 
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