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Old 11-03-2006, 09:54 PM   #1 (permalink)
icer97
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injector pump leaking fuel at throttle shaft

Well ive had the hard start problem now for a while. I replaced the lift pump with electric and intalled all new glow plugs along with a new manual relay. So I performed the test posted here by putting 6 lbs of vacuum on the return line nose. I was not able to get enough pressure because my fuel cap was leaking. After curing that and getting 6 or so psi of fuel pressure on a guage I tapped into the feed line I then looked for leaks. I finally found fuel dripping from my throttle shaft on my injector pump. Am I getting air in the system after the truck sits a while from here? Looks as if a pump R&R is in order. What kind of pressure does that seal have on it while running, lift pump pressure, or actual high IP pressure? I have no way to time the pump after removing, can a man get close enough by just taking a chissel and marking the IP and the timing cover? Will this get her in the ball park? Thanks alot 6.2 diesel guru's!
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1976 Chevy shortbed converted 1 ton, 383 stroker, 400 trans, 205 gear drive, 14 bolt,dana 60 both with 4:56 gears and detroit and powertrax lockers sitting on 40's its my mud toy!

1984 Chevy CUCV 1 1/4, 6.2 diesel, 400 trans, 208 transfer 14 bolt, dana 60 4:56 gears, blackout lights work and everything!

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Old 11-03-2006, 11:01 PM   #2 (permalink)
High Sierra 2500
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Well, sounds like the pump needs to be rebuilt... It is probably the cause of your starting issues if there is nothing else leaking. The seal doesn't have really high pressure on it.

There should be timing marks on it already... These are from the factory. They are initial settings, really... After it is running it should be dynamically timed using a timing light. There is really no point to making marks so you can reinstall the pump the same way... After all, you will probably end up with an exchange pump which won't have the marks on it... Or if you get your pump back it may end up set up differently anyway. You will have to start with the initial settings (timing marks lined up) and go from there.

Hope this helps!
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Old 11-04-2006, 10:16 AM   #3 (permalink)
jdemaris
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Could be easy?

Quote:
Originally Posted by icer97;1391672;
Well ive had the hard start problem now for a while. I replaced the lift pump with electric and intalled all new glow plugs along with a new manual relay. So I performed the test posted here by putting 6 lbs of vacuum on the return line nose. I was not able to get enough pressure because my fuel cap was leaking. After curing that and getting 6 or so psi of fuel pressure on a guage I tapped into the feed line I then looked for leaks. I finally found fuel dripping from my throttle shaft on my injector pump. Am I getting air in the system after the truck sits a while from here? Looks as if a pump R&R is in order. What kind of pressure does that seal have on it while running, lift pump pressure, or actual high IP pressure? I have no way to time the pump after removing, can a man get close enough by just taking a chissel and marking the IP and the timing cover? Will this get her in the ball park? Thanks alot 6.2 diesel guru's!
The shaft seals are under constant low pressure - via a housing fuel pressure regulator - usually under 10 PSI. All the seals are - are o-rings and teflon backup washers. When that pump is mounted on an engine that's easy to get to - it's a ten-minute job to pull the shafts out and put in new seals. But - on the 6.2s? Although I have many, can't say I ever tried to replace the seals with the pump still mounted. To get to the seals, top cover comes off the pump, a little internal lock-clip is removed, and then the shaft(s) - which is actually two halves that locked together - pull out of the pump sideways. My 7.3 Ford diesel has been leaking a little in same place and I might attempt fixing it soon (it has the same pump). But - it's a minor issue - I'd worry more about fuel residue building up and having a fire.
In regard to those leaking seals letting air in and causing a starting problem - NO. Even if they leaked so bad that the pump internal housing emptied down to the level of the shaft - all the important pump parts would still be submerged in diesel. I've run many pumps with the cover off and the housing half-empty. High pressure fuel does not affect the low-pressure in the housing - unless a return line is plugged. When that happens, the engine usually quits - and acts like it's running out of fuel - even though that is not really the cause.
The timing you mention - i.e. the "static" or "initial" timing is not that critical. Mark it any way you can and put it back the same. Keep in mind that such timing specs. given by GM are generalizations - and not custom tailored to every engine. Engines differ when old and new - due to a wide-range of machining tolerances and wear - especially timing-chain wear. So, usually, for best performance and starting - time it by "ear." But, I guess you also have to keep in mind that such timing is quite different than the timing -advance. The pump is supposed to automatically advance the timing as load and/or RPM increases. So, let's say it is engineered to advance 6 degrees by 1500 RPM. And, you bump up the intial (non running) timing by 3 degrees. Then, the final advance will also be bumped and be 9 degrees instead. When those pumps are used on some industrial and farm equipment that advance is easily adjusted independent of the initial timing via a trimmer-screw. Not the case when used on the 6.2 GM or 6.9/7.3 Ford IH.
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Old 11-04-2006, 10:53 AM   #4 (permalink)
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Quote:
Originally Posted by jdemaris;1392221;
The shaft seals are under constant low pressure - via a housing fuel pressure regulator - usually under 10 PSI. All the seals are - are o-rings and teflon backup washers. When that pump is mounted on an engine that's easy to get to - it's a ten-minute job to pull the shafts out and put in new seals. But - on the 6.2s? Although I have many, can't say I ever tried to replace the seals with the pump still mounted. To get to the seals, top cover comes off the pump, a little internal lock-clip is removed, and then the shaft(s) - which is actually two halves that locked together - pull out of the pump sideways. My 7.3 Ford diesel has been leaking a little in same place and I might attempt fixing it soon (it has the same pump). But - it's a minor issue - I'd worry more about fuel residue building up and having a fire.
In regard to those leaking seals letting air in and causing a starting problem - NO. Even if they leaked so bad that the pump internal housing emptied down to the level of the shaft - all the important pump parts would still be submerged in diesel. I've run many pumps with the cover off and the housing half-empty. High pressure fuel does not affect the low-pressure in the housing - unless a return line is plugged. When that happens, the engine usually quits - and acts like it's running out of fuel - even though that is not really the cause.
The timing you mention - i.e. the "static" or "initial" timing is not that critical. Mark it any way you can and put it back the same. Keep in mind that such timing specs. given by GM are generalizations - and not custom tailored to every engine. Engines differ when old and new - due to a wide-range of machining tolerances and wear - especially timing-chain wear. So, usually, for best performance and starting - time it by "ear." But, I guess you also have to keep in mind that such timing is quite different than the timing -advance. The pump is supposed to automatically advance the timing as load and/or RPM increases. So, let's say it is engineered to advance 6 degrees by 1500 RPM. And, you bump up the intial (non running) timing by 3 degrees. Then, the final advance will also be bumped and be 9 degrees instead. When those pumps are used on some industrial and farm equipment that advance is easily adjusted independent of the initial timing via a trimmer-screw. Not the case when used on the 6.2 GM or 6.9/7.3 Ford IH.

Sounds like you have a great deal of knowledge on the Stanadyne ip used in the 6.2. Maybe you could post a thread on rebuilding it. That could save all of us some serious coin the next time the ip needs a rebuild.
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Old 11-04-2006, 11:07 AM   #5 (permalink)
84Sierra
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I'd love to see how to rebuild one of those. I would for sure try it myself when I need to. Hook us up! Stickies help out a lot. Kinda like our own backyard manual.
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Old 11-04-2006, 02:44 PM   #6 (permalink)
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Quote:
Originally Posted by jdemaris;1392221;
To get to the seals, top cover comes off the pump, a little internal lock-clip is removed, and then the shaft(s) - which is actually two halves that locked together....
The pump is supposed to automatically advance the timing as load and/or RPM increases. So, let's say it is engineered to advance 6 degrees by 1500 RPM. And, you bump up the intial (non running) timing by 3 degrees. Then, the final advance will also be bumped and be 9 degrees instead. When those pumps are used on some industrial and farm equipment that advance is easily adjusted independent of the initial timing via a trimmer-screw. Not the case when used on the 6.2 GM or 6.9/7.3 Ford IH.
Well, you do sort of have an idea how Stanadyne rotary pumps work, but let me fill in some of the blanks for you...
First ALL automotive DB2 pumps (6.2, 7.3 etc) use a single piece throttle shaft. So there is no split in the middle like on off highway pumps, the automotive pumps also have a face cam on the throttle shaft, opposite the throttle lever.
So to remove the throttle shaft on a DB2 pump, in addition to removing the intake manifold and top cover, you have to remove the guide stud that holds the governor spring body in place, remove the screw that holds the face cam in position, which means if you have an automatic tranny, you will also have to mark/remove the Throttle position/ kick down sensor, and then slide the driveshaft out. Taking it apart is easy, putting it together and making sure it won't leak again is tricky on the truck.

First you have to make sure that you're pump doesn't have the old style brass throttle lever bushings, if it does, don't bother replacing the seals, I guarantee it will still leak. Next, you have an adjustable guide stud, there will be a small red spring inside the governor contol body that you removed, and when you remove it, the spring falls right into a hole in the top of the cam ring, and there will also be a thrust spring on the driveshaft to hold tension against the governor body.

Next you have to carefully replace the seals on the driveshaft, don't worry about the spacer on the lever end, and make sure you don't drop the white nylon washer on the face cam end. And I hope you marked where the face cam was when you started, the best way to do this on the vehicle, is hold the throttle in Low Idle position, and mark how high the back of the face cam is above the rear. You need to get it as close as you can to the way it was when you took it apart, this setting controls how fast your Light Load Advance moves, otherwise you could have white smoke at idle or while cruising. Also, if you have an adjustable guide stud, you will need to note the distance between the top of the adjusting nut and the head of the guide stud and return it to the same dimension when you reinstall it to ensure you get the same high idle (cut off) speed.
Also, when you replace the top cover, you HAVE to make sure you get the arm on the shutoff solenoid on the front side of the governor linkage, otherwise the engine WILL run away.

If your pump is leaking out the throttle shaft, that pretty much means all the seals inside need to be replaced. If your throttle shaft or housing is worn out, then you won't fix the leak by changing the seals. A trained technician would be able to determine what parts are in need of replacement, not only to fix the leak and make sure it stays fixed, but also replace any other worn parts and re-calibrate to get it back to factory performance and reliability.

My advice, leave fixing leaks on your injection pump to guys like me.

Also, is the truck hard start hot (after it has been running a while and restarted within half hour) or cold (first thing in the morning) or both?
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Old 11-04-2006, 07:39 PM   #7 (permalink)
jdemaris
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To Texas diesel guy

Quote:
Originally Posted by Texas Diesel Guy;1392504;
Well, you do sort of have an idea how Stanadyne rotary pumps work, but let me fill in some of the blanks for you...
Also, is the truck hard start hot (after it has been running a while and restarted within half hour) or cold (first thing in the morning) or both?
I have more than "sort of an idea" as you put it. But, the bulk of my experience as a bench tech. was industrial and forestry - not automotive - all of our Roosamaster/Standadyne pumps being DB, JDB, DC, JDB, C, or DB2. Also some rotary CAV - and CAV bought their design from Roosamaster.
I doubt there is much you're going to tell me about the history of Vernon Roosa and the rotary pump he invented - and its theory of operation that makes it unique. Now -about details on automotive applications - yes. Some details differ, but the principle of operation is the same - and as I said earlier - I haven't even bothered to fix my own since slight leakage is not an issue to me. I would not attempt to write a tutorial in this forum on pump theory, design, and repair. It is just too difficult to do - without photos, detailed written instructions, and hands-on experience.
My point of my post was - and is - that slight leakage at the shaft-seals is not going to create the starting problem the guy described and I was trying to get him on the right road to diagnosing his problem.
And - about leaving it to "guys like you" - that's fine in most cases. But - I assume that there are some people here interested in doing some things themselves. And, there is nothing that esoteric inside a fuel-injection pump that makes it more difficult than properly rebuilding a engine, a closed-center hydraulic pump, etc. The main issue with injection pumps and repair is the lack of access to detailed repair information to the general public. You can call it anything you want, - but it is - basically just a low pressure pump hooked to a high pressure pump with several controls for flow, timing,RPMs, etc. There are many situations where a pump can be quickly repaired for $50 in parts and two hours work - but - instead gets sent out and with a price of well over $300 instead.
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Old 11-04-2006, 07:56 PM   #8 (permalink)
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Texas Diesel Guy. None of us here are looking to take anyone's job. It's just that most of the folks posting on the 6.2 forum aren't exactly in the money. If we were I doubt we would still be driving trucks from 82-92. If it really is something beyond the do it yourselfer then so be it. Just thought I'd ask. From what you've said it seems like a common rail system is actually much simpler from a mechanical standpoint.
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Old 11-04-2006, 08:40 PM   #9 (permalink)
icer97
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Thanks for all the replys! My starting problem is when its cold only. Especially when first started, or after its sit an hour or so. After its been started it starts fine. Even on a 90 degree day after its sit an hour I have to crank and crank or give her a shot of you know what to get her fired. Everytime I crack the fuel bleeder, air is in the system. This is why I performed this test, but the throttle shaft is the only leak ive found. I thought maybe it was getting air in the system after it was shut off from the throttle shaft. If its not, im not worried about a little leak, it doesent leak enough to even have raw fuel laying on the intake, its just always wet looking. Can this be causing air to get in my fuel system??
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1984 Chevy CUCV 1 1/4, 6.2 diesel, 400 trans, 208 transfer 14 bolt, dana 60 4:56 gears, blackout lights work and everything!

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Old 11-04-2006, 09:55 PM   #10 (permalink)
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Look again if you've got air at the bleed valve... Even if the throttle shaft seal is causing problems, you certainly wouldn't be getting air at the bleed valve.

I think you need to perform the test again... Look very, very carefully for leaks.


If you still can't find anything after that:

Hook an air line up to the hose connection on the air bleed valve. Open the bleed valve and apply air pressure. This will blow all the fuel out of the lines and into the tank. Get all the fuel out of them. Close the bleed valve and unhook the air hose.

Now perform the air pressure test as normal, but this time, while the lines are pressurized, take a cup full of soapy water and use a paintbrush to brush it on the fuel lines... Look for bubbles. Bubbles signify a leak. When you are done, leave the lines pressurized and crack open the bleed valve until you get fuel to bleed the system out.

Hope this helps!
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