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Rob

Endt865b (v8)

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Here is a new dilema for me. I've never been around one of these engines until now. It starts and idles for about a minute just short of perfect. This is either hot or cold, but after a short bit of time the idle speed varies up and down between 400-650 rpm consistently. It will probably do that all day if left alone that long. If the engine is manually held at a high speed, (say 1000 rpm) and then let back to idle, the engine seems to want to run at about 700 or so rpm for about a minute, then back to the varying idle once again. I have also noticed tonight that when the engine is rapidly revved from low idle by floorboarding the accelerator, the engine seems to have a lazy cylinder. I really can't call it a miss, but at least one cylinder seems to be a bit weak. This of course is just assumption. I will in the near future run a compression check on all cylinders to verify this assumption. I'm going to change all the filters within the next week just before the compression check to have a valid baseline to start with.

Would a leaking/dripping injector cause this problem, or does it sound more injection pump related? Regardless, if the compression check is good, the problem would have to lie within the fuel system. I do not suspect air entrainment as the engine does not even roll the cooling fan over a compete revolution before starting.

Thanks,

Rob

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Hi Rob - We used to have a similar problem caused by worn governor weights in the Ambac Injector pumps in the 237 and 285 Maxidynes. The revs would roll from 500 to 1000 rpm while they stood there. It changed when you parked on a slope with the front of the truck either up hill or down hill - I don't remember which. We used to re-bush the weights and put new bearings in the governor and it would fix it up. I don't know if the V8 has a similar governor, but it sounds like the same thing. Best regards - Michael.

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Hi Rob - We used to have a similar problem caused by worn governor weights in the Ambac Injector pumps in the 237 and 285 Maxidynes. The revs would roll from 500 to 1000 rpm while they stood there. It changed when you parked on a slope with the front of the truck either up hill or down hill - I don't remember which. We used to re-bush the weights and put new bearings in the governor and it would fix it up. I don't know if the V8 has a similar governor, but it sounds like the same thing. Best regards - Michael.

Hi Michael, I had never thought about the governor being in the mix. That would make sense as the fuel rack could likely be pushed and pulled due to flyweight(s) not being stable because of wear.

The injection pump looks just like a small V8 with a "valley" in the middle of the pump towards the front of the truck. The rear (governor) looks almost the same as an American Bosch, or AMBAC pump on an inline engine. It just bolts to the rear of the pump housing just as the inline engine does.

Thanks, and I'll keep you posted.

Rob

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It is definately governor related, my EM6-300 did the same thing until I installed the fuel rack "patch" kit to stop the bouncing at highway speeds. All it consists of is a very light spring and a roll pin in the fuel rack.

Jeff

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I've seen this problem on engines with low oil presure.

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I've seen this problem on engines with low oil presure.

Thanks David. The oil pressure is never below 35psi at 400 rpm, and is about 75-80 psi at 1000 rpm.

Rob

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It is definately governor related, my EM6-300 did the same thing until I installed the fuel rack "patch" kit to stop the bouncing at highway speeds. All it consists of is a very light spring and a roll pin in the fuel rack.

Jeff

Not oil preasure related on this engine!

this is comon to the ambac pump !The governer is your culpret!The problem can be addressed by a (GOOD) fuel shop,

The governer can be removed and repaired for less than 1000 bucks!

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Not oil preasure related on this engine!

this is comon to the ambac pump !The governer is your culpret!The problem can be addressed by a (GOOD) fuel shop,

The governer can be removed and repaired for less than 1000 bucks!

I spoke with a gentleman referred here and he was very much aware of this problem. I'm going to pull the pump and nozzles and get them sent off to be done right. I don't need problems in the future!!

Thanks,

Rob

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I spoke with a gentleman referred here and he was very much aware of this problem. I'm going to pull the pump and nozzles and get them sent off to be done right. I don't need problems in the future!!

Thanks,

Rob

Rob be sure to set the engine on the timing marks BEFORE you pull the pump!This can be done by removing the little rectangle cover in front of the fuel pump and look for a small hole in the pump drive hub! Centre the hole in the window!

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Rob be sure to set the engine on the timing marks BEFORE you pull the pump!This can be done by removing the little rectangle cover in front of the fuel pump and look for a small hole in the pump drive hub! Centre the hole in the window!

Well, curiosity got the best of me and I pulled the governor from the back of the pump without removing the pump from the engine. Really a simple little contraption but took some engineering to make work.

Long story short is that $65.00 bought me new bushings, shafts, seals and gaskets, springs, and a good set of installation and calibration proceedure(s) from the local fuel injection shop.

Along the same lines as Michael had mentioned; I put the front axle in a ditch out front of my shop and the truck ran very smooth, and stable, without fluctuation at idle. I was surprised how smooth it actually is. It accelerates very well but at 40 MPH, it is hard to keep in one lane. The tie rod ends, and drag link are shot, shot , shot.

Since this truck will ultimately end up with my detroit engine, I really don't want to sink a lot of money unnecessarily into this V8.

Appreciate all the advice!!

Rob

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Well, curiosity got the best of me and I pulled the governor from the back of the pump without removing the pump from the engine. Really a simple little contraption but took some engineering to make work.

Long story short is that $65.00 bought me new bushings, shafts, seals and gaskets, springs, and a good set of installation and calibration proceedure(s) from the local fuel injection shop.

Along the same lines as Michael had mentioned; I put the front axle in a ditch out front of my shop and the truck ran very smooth, and stable, without fluctuation at idle. I was surprised how smooth it actually is. It accelerates very well but at 40 MPH, it is hard to keep in one lane. The tie rod ends, and drag link are shot, shot , shot.

Since this truck will ultimately end up with my detroit engine, I really don't want to sink a lot of money unnecessarily into this V8.

Appreciate all the advice!!

Rob

Good job Bud!

The hardest part is geting the both racks engaged into the yoke!If ya miss one side you can have a big oh shit on your hands! Beender dondhat.

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Good job Bud!

The hardest part is geting the both racks engaged into the yoke!If ya miss one side you can have a big oh shit on your hands! Beender dondhat.

I can sure see how that would be a problem. Before pulling the governor assy. from the pump, I viewed the area with a small inspection mirror, (lighted) and then squeezed the arms of the yoke together just enough for the "doglegs" of the yoke arms to barely disengage the racks. It will probably be a little more difficult to reinstall so I will enlist a third hand via my daughter.

I also noticed the thrust/roller bearing is a little notchy in operation so I have ordered another to be on the safe side. This should be in on Monday and I hope to reinstall the parts early next week.

I'll try to get some pictures up as I'm sure others have never seen the internals to one of these either.

Thanks again for the help!!

Rob

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I can sure see how that would be a problem. Before pulling the governor assy. from the pump, I viewed the area with a small inspection mirror, (lighted) and then squeezed the arms of the yoke together just enough for the "doglegs" of the yoke arms to barely disengage the racks. It will probably be a little more difficult to reinstall so I will enlist a third hand via my daughter.

I also noticed the thrust/roller bearing is a little notchy in operation so I have ordered another to be on the safe side. This should be in on Monday and I hope to reinstall the parts early next week.

I'll try to get some pictures up as I'm sure others have never seen the internals to one of these either.

Thanks again for the help!!

Rob

It may have a barrel and plunger sticking but any way it needs pulled and put on a test stand. glenn

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It may have a barrel and plunger sticking but any way it needs pulled and put on a test stand. glenn

I agree Glenn. The injection shop I'm working with does not have the correct adapter to "spin" this particular pump. If it still presents any problems upon reassembly it will come off and go in the mail to another shop I've spoken with.

Thanks,

Rob

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Good job Bud!

The hardest part is geting the both racks engaged into the yoke!If ya miss one side you can have a big oh shit on your hands! Beender dondhat.

Well tonight I reinstalled the rebuilt governor assembly back on the truck. As king Richard used to say, "Man, What A Difference"!! There is a bit of a lengthy story to get to this point so bear with me through the details:

Upon dissassembly, the flyweights were found to already have oversized pins installed and the correct bushings were no longer available, and these were worn out. In fact when the pump was rebuilt once before with new pins installed, one of the oiler holes was not lined up properly so the pin and arm was starved for lubrication from the get go. Long story short is that I rebored, and reamed the holes in the flyweight(s), made new bushings to fit the new pins, installed new springs and thrust bearing, then hand cut the top, and rear cover gaskets, (they are no longer available). The gasket that sandwiches between the governor housing and the main pump body is still available, but at a different thickness necessitating fuel rack adjustment(s). As FJH said, it was a real somebitch to get the yoke back into the fuel racks. It sure was easier to get it apart!!

The engine now idles/runs steady at 725rpm with both the compressor running, and off. Off idle response is great. I need to shorten the adjuster on the throttle linkage as the engine will run much slower with this linkage disconnected. I've already run the idle adjust screw out as far as possible. It's determined the gasket at the governor housing is causing this as it is nearly 3 times as thick as the original. There is plenty of room for adjustment through the linkage.

Really appreciate the help and all the pointers here. I've got about 8.5 manhours into this thing but I usually work cheap on my own stuff. Besides, I've learned quite a bit and that is basically a miracle, (the learned part).

Thanks again,

Rob

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Rob,

After all this work - you might even be tempted to leave the Detroit by the curb where it belongs.

--- just kidding, of course.

Paul Van Scott

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Rob,

After all this work - you might even be tempted to leave the Detroit by the curb where it belongs.

--- just kidding, of course.

Paul Van Scott

I dunno there Paul; I've sure turned down a few offers on both the Detroit, and the Mack engines. If this Detroit engine that I have was not so damn "familiar" to me, I would just leave the V8 in place. This truck really runs out well, but the front end is very sloppy due to tie rod ends being shot. Under 40MPH and it is alright on smooth pavement but above that is anybody's guess.

I absolutely despise the six speed transmission because of the shifter "slop". I purchased a reman RTO-12513 from a Mack RW-613 and will try to get it installed before the end of August. Time is short right now with all the construction projects going on at work so I don't get to "piddle" in the shop much.

Hope you're doing alright and making progress with your Mack. Keep me posted on the drive axle from Tulsa. Tell your uncle I said hi.

Rob

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Well tonight I reinstalled the rebuilt governor assembly back on the truck. As king Richard used to say, "Man, What A Difference"!! There is a bit of a lengthy story to get to this point so bear with me through the details:

Upon dissassembly, the flyweights were found to already have oversized pins installed and the correct bushings were no longer available, and these were worn out. In fact when the pump was rebuilt once before with new pins installed, one of the oiler holes was not lined up properly so the pin and arm was starved for lubrication from the get go. Long story short is that I rebored, and reamed the holes in the flyweight(s), made new bushings to fit the new pins, installed new springs and thrust bearing, then hand cut the top, and rear cover gaskets, (they are no longer available). The gasket that sandwiches between the governor housing and the main pump body is still available, but at a different thickness necessitating fuel rack adjustment(s). As FJH said, it was a real somebitch to get the yoke back into the fuel racks. It sure was easier to get it apart!!

The engine now idles/runs steady at 725rpm with both the compressor running, and off. Off idle response is great. I need to shorten the adjuster on the throttle linkage as the engine will run much slower with this linkage disconnected. I've already run the idle adjust screw out as far as possible. It's determined the gasket at the governor housing is causing this as it is nearly 3 times as thick as the original. There is plenty of room for adjustment through the linkage.

Really appreciate the help and all the pointers here. I've got about 8.5 manhours into this thing but I usually work cheap on my own stuff. Besides, I've learned quite a bit and that is basically a miracle, (the learned part).

Thanks again,

Rob

You da man Rob! Agian good job !Idle should be set at 650 I hate it when they idle fast! :)

Edited by fjh

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You da man Rob! Agian good job !Idle should be set at 650 I hate it when they idle fast! :)

Hi Rob - Its great that you got it going well. In 1982 I got caught with the same problem as I said before. I took my pump to Mack Trucks in Brisbane and they charged me over $1200 to fix it and they did not even put the pump on the test bench. Since then we have done the same job ourselves for about $100 each time with the same results and you don't have to pull the pump off. Did you check the gear levers and selectors on your gearbox. If the lever is sloppy you may be able to build them up again. It might only need the bottom of the gear levers building up, which doesn't take very long to do. Best regards - Michael.

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hey Rob,

You need to make time to come on over to the Elnora show in Sept...... That goes for all of you on the board too!! Need to keep the "R-12" operational, maybe you could take it to the show(Hint-Hint)

I thought the v-8 ran good as it was so it's got to run FANTASTIC now...

Fred

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hey Rob,

You need to make time to come on over to the Elnora show in Sept...... That goes for all of you on the board too!! Need to keep the "R-12" operational, maybe you could take it to the show(Hint-Hint)

I thought the v-8 ran good as it was so it's got to run FANTASTIC now...

Fred

Hi Fred, great to see you post on the board again! The V8 really does run well now. Spent about an hour and a half yacking with the fuel injection guys about matching pump and turbo outputs today and giving thanks for their guidance with my governor. With their recomendation, I'm going to cut the fuel back just a bit as I don't want anything on a trailer painted black from the smoke!! Also wanting to install the 13 speed later this month and get some license plates, so the future is looking brighter!

I'm planning to make the show at Elnora this year, (with this Mack) but first I've got to do something about the wiring. I don't feel it would be wise to trust the current installed harness. Don't expect any changes in the trucks outside physical appearance by then, I've not had much free time lately.

Talk to you soon!

Rob

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Hi Rob - Its great that you got it going well. In 1982 I got caught with the same problem as I said before. I took my pump to Mack Trucks in Brisbane and they charged me over $1200 to fix it and they did not even put the pump on the test bench. Since then we have done the same job ourselves for about $100 each time with the same results and you don't have to pull the pump off. Did you check the gear levers and selectors on your gearbox. If the lever is sloppy you may be able to build them up again. It might only need the bottom of the gear levers building up, which doesn't take very long to do. Best regards - Michael.

Hi Michael and FJH, I wanted to say "thank you" to you both personally as your input was the inspiration to make this thing right. All of the input received was positive inspiration as I have a hard time living with something that is not "quite right". If I have an inkling of bettering something, I usually jump right in. It really was fairly easy to machine the new parts but I have access to the needed tools/equipment.

I have not checked the lower ends of the shift levers but what is sloppy is the "slots" in the shifter ball or the guide pins are worn/broken. The transmission gear selector, (5 speed handle) has a lot of rotation available instead of a nice front to back and side to side motion. The transmission shifts fine, and once used to the power curve of this engine, it is not that bad. I could live with it but the cab is a bit cramped and my wife is going to attend the truck shows with me so I need all the room in the cab, (for baggage, not her) I can get!!

Thanks again,

Rob

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You da man Rob! Agian good job !Idle should be set at 650 I hate it when they idle fast! :)

Man, I've got to quit reading this board so late at night....... I find it hard to sleep when I'm grinding on an idea. I arrived to the shop early this morning about 5:30 am and took after the throttle linkage. It adjusted right down to stalling the engine if I wanted to. Ultimately, it idles at 644-648 rpm via my hand held electronic tachometer, (it is accurate). If the engine is revved to approximately 1000 rpm, and the throttle released, the engine decelerates to 639-641 rpm and immediately stabilizes at the above mentioned figures. I did not realize that a mechanical governed engine would be that "tight" in speed regulation. I maintain standby powerplants so speed regulation is familiar to me.

Now when my tool bit for the leaking buttess screw shows up.........

Rob

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