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Injection pump adjustments/modifications

27K views 36 replies 8 participants last post by  FordGuy100 
#1 ·
Is there a way to change the governed rpm limit on a 7.3l turbo? mine seems to cut out at only 2900 to 3000 rpm. ive seen places where they build a pump calibrated for turbo(factory or not) that has the rpm limit at 3800 rpm. I was just wonderin if there was a way to adjust the pump i have. the pump is a XX31 model not the XX29. any help would be greatly appreciated!
 
#2 ·
To raise the rpm you need to change the governor spring under the top cover. The one from a 6.2 GM will put you at approx. 4000 rpm. The one from a 5.7 GM will put you around 4400 rpm. You could also shim the governor spring for ?? rpm.

I run 6.2 spring in mine and am fairly happy with how it runs.
 
#3 ·
hmm i need to get me one of those. mine is pulling fuel at 3k.
 
#4 ·
it just so goes that i have an injection pump from a 92 6.2l from my old truck when i blew up the motor! had no idea that that is what does it. What is involved in changing this spring? i know that you have to be careful when messing with the screw there! thats how i blew my old 6.2l. turned the timing advance and it ran away on me. didn't know how to shut it down at the time! blew up in the barn
 
#5 ·
To change the spring you remove the top cover. There will be a block and shaft( might be poor desciption) with 2 springs on it. This is the governor assembly connected to the throttle shaft. Remove the guide pin ( screw at the back of pump with locknut) as it runs thru the center of the governor assembly. Count the number of turns to remove the guide pin as it is also an adjustment that you'll want to put back close to original. Once the guide pin is removed you can slip the governor out from under the shaft Be careful there is a small spring in the center of the governor you don't want to lose. Now if you have the whole governor out of the 6.2 pump you can just install it. If you only have the spring (which is the larger of the 2 on the governor) you'll have to unscrew the governor assembly to swap the spring. Again count the number of turns because the overall length of the governor effects idle rpm. When you reinstall the top cover make sure the FSS is properly engaged or you may have a runaway when you fire it up. I slide the cover on from front to rear and have never had a problem, or you can just apply 12v to the FSS if it clicks then it should be engaged properly.
 
#6 ·
OR you could just adjust it the proper way and just back out the high idle screw on the throttle lever. That way you don't have to worry about takeing anything apart on the pump and you won't screw with your regulation by putting in the wrong spring or governer. The 6.2/6.5l min/max assemblies (the "block and shaft" described above) are completely different than the ones on the 6.9/7.3s. They are two piece and don't have a spring in the middle of them and they don't have a return spring on the throttle shaft for them either.

Anyway back the screw out on the throttle shaft that is on the back side of the throttle lever. So it's the one on the side of the pump as the fuel inlet cone. Back it out a half a turn or so at a time until you get the rpm you want. But be careful not to go to far and over rev it. If the pump has any kid of warranty this will void it as they usually either have a seal wire and or some laquer on them so the fuel shops know if you have tampered with it.

That being said if there is runability issues and it's not reving out to the proper RPM then it might be a good idea to pull the pump and have it gone through.
 
#7 ·
Thanks for all the help. i am hesitant on unscrewing anything in that area as i had bad luck with results before. Can some one find me a picture of the underside of the cover from the pump? i have seen it before but it would be nice if you guys could point out the different parts you listed. thanks
 
#8 ·
Adjusting the screw on the throttle shaft is not going to change the rpm that the pump goes into defueling/ fuel cut. If your pump isn't going into fuel cut then adjusting that screw will get you more rpm. Remember if the screw on yours has the laquer unbroken on it then it should be set to the correct Stanadyne spec. So adjusting it wouldn't be considered the proper way either. I remove my 6.2 springs from 6.2 pumps. I could be wrong about the whole assy. fitting in the 6.9/7.3 pumps as I forgot about the return spring issue. I have always just swapped the max governor spring. At any rate the 6.2 spring fits the 6.9/7.3 governor perfectly and is how the few I know of who build HP DB2 pumps raise the rpm limits of the pump.:shrug:
 
#9 ·
Ok not trying to be a jerk or anything but when was the last time you actually overhauled a complete DB2 pump and when was the last time you ran one on a calibration stand? It would be last week for both for me. I work in a fuel shop and overhaul those pumps all the time. The throttle lever is more or less and rpm selector. The farther it moves foreward the more rpms it will give. At ANY throttle position you will get full load fuel if the engine rpm is less than desired for that position. To set the high idle on these pumps, which is the max rpm, you adjust the high idle screw on the throttle lever.

The governer spring does NOT effect RPM but rather governer regulation. Regulation is the rpm range that it goes from full load fuel to no fuel. For example if you want 5% regulation at say 2000 rpm you would go from full load fuel at 2000 rpm to no fuel at 2100 rpm. If you wanted 8% regulation at 2000 rpm you would have full load fuel at 2000 rpm and no fuel at 2160 rpm. The different spring tensions change the percentage of regulation. NOT the high idle rpm.

You are correct that if the laquer is not disturbed the setting is at what stanadyne or the last fuel shop set it at to be calibrated for the proper rpm. That's why I said before that if you're not getting full rpm out of it you may have something else wrong with it and it may need to be overhauled.
 
#10 ·
You're not being a jerk your just trying to explain something that it seems you know more about than me. That's fine.

Does the screw on the throttle shaft effect when it goes to no fuel/ fuelcut or does the governor spring?

gtspowerstroke said:
The governer spring does NOT effect RPM but rather governer regulation. Regulation is the rpm range that it goes from full load fuel to no fuel.
This statement tells me that if I take a pump that is functioning properly and goes from full fuel at 3000 rpm to no fuel at lets say 3300 and I change out the spring I will get more rpm out of it. Now all the stock spec IDI pumps I've had experience with gone to nofuel somewhere between 3300 and 3600. The original poster was asking about pumps he saw that were rated at 3800 which would mean no fuel at around 4000-4180? Now the way I know to get those rpm numbers is to change the spring becuase backing that crew out has never got me 3800+ rpm. How would you get a IDI spec DB2 to allow 3800 or more rpm?
 
#11 ·
OK so on the test stand you can run it at any rpm because the pump isn't running the RPM. So you can run it up to the high idle that gives no fuel. However when the pump is operating on the engine once it hits that max rpm where the governer starts to cut back it will keep cutting fuel back until the engine doesn't make enough power to spin any faster. So it will constantly bring it back to that same rpm. It won't let it go the extra 100 rpm or what ever the regulation is.

That being said by changing the spring it will effect the tension on governer and change the rpm slightly but it really won't do what you are looking to do. Ultimately to just adjust the high idle screw is the simplest way and the proper way to adjust the rpm that the governer starts to kick in.
 
#12 ·
Ok. On the last pump I had built at a well respected pump shop which is a db2829 4369 ( at least I think it was a 4369) I couldn't get much more than 3200 rpm 3000 was all it really wanted to do. That was with the screw backed out as far as it would go and still make contact with the stop. I then installed one of my 6.2 springs with no other changes and I could hit 4000. Why is this?
I mean this is a large difference. I have changed the spring in a few others with the same basic result always being able to reach approx. 4000 rpm no matter what the pump would originally reach.
It appears that you know more about these pumps than me. I'm just trying to relate my experiences with how you are saying it works.
 
#13 ·
Hmm.... I may have to take a look at the springs and see what they are. It could be that the other springs are a LOT stiffer so it just takes the governer that much more to compress them. Or they may be longer giving the same result. Did you change the spring or the whole assmebly? I think the 6.2 and 6.4s are set up to run a little higher rpm but I'd have to take a look at a couple pump specs to verify that.
 
#14 ·
I just change the spring.

It is my understanding from the few pump builders who are willing to talk about pumps that changing the spring is how they get large increases in rpm. That's how I learned about the 6.2 spring from a guy building pulling tractors in Colorado. From what I have seen is the 6.2 spring will give you 4000 or so rpm and one from a 5.7 will give you 4400 rpm.

I am no pump expert but I have been farther into my pumps than most. What I know and understand is the high idle screw might give you a couple hundred more rpm but a spring change will give you the large increases.:shrug:
 
#15 ·
but is it safe to run 4000 rpm with this motor? now im wondering if it helps that much to have it rev that much. it makes hp at 3000 so would it really be beneficial to go to 4000? i dont think that my stock motor can take 4000rpm maybe 3600-3700 but i think 4000 is way too much. i am still interested in doing something though to get me a little higher. can i shim the spring if that is what controls rpm? what would i shim it with?
 
#16 ·
If you are takeing the engine and pump so far out of it's designed operating range which is most likely what's happening with your friend with the pulling engines then you are going to have to do more than just adjust the high idle screw. Insalling a much stiffer spring would do that. I don't think the original poster is looking to do that though. For a few more rpm then the high idle screw is the quickest, easiest, and most proper way to do it. For a LOT more rpm then you are most likely going to have to change a lot more.

Sootman if you want more rpm then just adjust the high idle screw as I described above. If you can't get more rpm out of it and it's not actually getting to the designed rpm limits then pull the pump and have it checked out. If you are just wanting to heavily modify it then you could put a spring in it and turn the fuel way up etc. etc. etc.
 
#17 ·
Well 4000 being safe is probably another debate. I've had 3 IDI trucks with combined mileage of over 900,000. Two of those motors have seen 4000 rpm on occasion. Typically I never run it much more than 3700-3800 and that's just when merging or keeping speed up on a hill with a large trailer. I've been told that Ken at DPS claims that 4000 is safe all day long on the factory balancing.You can believe what he says or not I usually don't The only reason I see being able to turn the motor faster than 3300-3600 in a daily driver is if you have 4.10s no OD and want to keep up with traffic.
 
#18 ·
wha? im going home and messing with mine. Although i think mine is just worn out. no load-3300 creeps to 3550. loaded i pulles hard to 300o then you feel it stop fueling..
 
#19 ·

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#20 ·
The screw with the lock nut and the redish laquer "seal" on it. Just break loose the lock nut and back the screw out some.
 
#21 ·
that would be correct.
 
#22 ·
just to be sure how far should i back the screw out? is there such a thing as too much? just wanna be sure before i do it. another thing. will i be able to use the extra rpm without my transmission shifting before it goes that high? i just ordered a banks transcommand tranny module. i was just wondering if i would have to reprogram shift points to take advantage of it. i will probably still do it just cause. i really thank you guys for your help with this issue!
 
#23 ·
i turned that screw all the way out but didn't get any change in rpm. im pretty sure i changed the right one. the one that is where the throttle cable is? at the top left corner of the top cover if the ip?
 
#24 ·
Sounds like you got the right screw. If the screw was already set for max throttle travel you won't gain anything by adjusting it. I personally have never seen a signifigant change by adjusting that screw though most are already set close to max travel anyway. You might have someone push down the throttle pedal while you watch at the pump to make sure your pedal and cable are giving you max travel. As long as your pump is in good shape the only other thing I know to do is changing things in the governor.
 
#25 ·
i went and looked at my pump. My screw isn't there. I have no idea how long its been gone too. i only rev to 3600 no load. it looses power at 3000 though. I bet my pump is worn out it hav 200k on it and its been maxed out for two years.
 
#26 ·
Mine has 200k on it too but it wont ever go higher than maybe 3100. dieselboy you say that you can rev it up in park or neutral to 3600? i dont think mine can go that high ever! im not sure though. i want to try changing the governor spring like 85hauler said. how hard is it to change?
 
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