Om603.971 3.5 vs 603.961 3.0 injection pump - PeachParts Mercedes-Benz Forum

rwd4evr · #1 09-13-2020, 05:17 PM

I can't get into my epc right now to look at elements and little parts in the injection pumps. I just scored a om606.962 from a e300td at the pull a part. Plan is to drop it in my w126 300sdl. So I have the pump from the 603.961 in my running car which may have a cracked head or slight head gasket leak. I also grabbed an injection pump from a 603.971 from a rod bender 3.5L w140 300sd(350sd really, early w140 cars were badged 300sd for some reason). Plans are for a diesel pump UK pump. For the time being I'm wondering if the 3.5 pump is a bigger element pump capable of more power on the 606? Since I've already got it loose In hand it makes sense to install it to test run the engine anyway. I need the rundown on cranking stock the 603 pump up all the way as well. It will be backed by a 6 speed 717.668 from a c230 kompressor too. So happy to have finally gathered all the bits. Been a long time coming. And the best part is ive got under 700 in the trans and motor.

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Diseasel300 · #2 09-14-2020, 01:03 PM

The pumps are the same internally. Same cam, same pumping elements, same delivery valves. The difference is in the fuel calibration, RPM limit, and torque-capsule adjustment. If you're planning to run the IP as it is, run the 3.0L pump, the 3.4L will strangle your engine above 4K RPM. To get the most out of the 606, you definitely want a properly built pump with bigger elements. The 606 breathes a lot better and needs more fuel than the 3.0L 603.

rwd4evr · #3 09-15-2020, 03:08 AM

Thanks for the more in depth on that, but the diesel pump UK guy basically said the same thing. 100hp at the wheels regardless of 603 or 606 on a stock pump. The positive is that he says my 716.668 6 speed is good at about 250hp which is where the stock turbo will run out of steam. So until later, either a gm,jeep or bmw trans adapter to handle the goods, and a hx35 or 40, the 400 hp pump(which he says is actually good for over 500 dependant on a few things) I'll be ordering will just basically be throttle stopped to keep it from rolling coal

. I'll throw the stocker on it to give it a little health check since just spinning it for compression won't necessarily let all the bad noises out. Then off it goes to Merry old England(or whatever) while I do timing chain tensioner, water pump and bottom end gaskets that he reccomended. He says pull a bearing cap too. Not sure I really want to do that though. I like to leave factory bearings alone. If it's not making noises and not garbage in the pan I'm content not knowing what they look like.

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Diseasel300 · #4 09-15-2020, 12:40 PM

Yes, the IP will give the same power output regardless of whether you have it on a 603 or 606. The injection quantity is the same, so the power output will be the same. Horsepower increase comes from additional fuel and timing. The difference between the 3.0 and 3.4 pumps is largely in the torque capsule and RPM limiting. The 3.0 pump will pull hard to ~4600 RPM before tapering off fuel while the 3.4L pump will fall on its face ~4K with the 3.0L engine. It's just how they're tuned for the different displacements.

The bottom end on the 60x engines is extremely durable. If there's no noise or symptoms of wear, leave well enough alone.

rwd4evr · #5 09-15-2020, 03:55 PM

Quote:

Originally Posted by Diseasel300

Yes, the IP will give the same power output regardless of whether you have it on a 603 or 606. The injection quantity is the same, so the power output will be the same. Horsepower increase comes from additional fuel and timing. The difference between the 3.0 and 3.4 pumps is largely in the torque capsule and RPM limiting. The 3.0 pump will pull hard to ~4600 RPM before tapering off fuel while the 3.4L pump will fall on its face ~4K with the 3.0L engine. It's just how they're tuned for the different displacements.

The bottom end on the 60x engines is extremely durable. If there's no noise or symptoms of wear, leave well enough alone.

Good to know about the rpm limit. I'm sure he deals with that in the pump build. My current 603 pull hard up to the 1-2 shift then kinda tapers off and i have to let off a touch to get 3rd before it falls on its face. I was hoping I could turn up the stock pump some before dishing out the $1000 or so with shipping and all that for the real deal. Yeah I get the fuel to power thing, makes sense if your not using all the possible airflow the head has to offer the 606 isn't going to make much difference. You can make pretty serious power with the 603 but the head cracking is a possible liability. I haven't gone propane on the 603 yet but it sure wakes up a 617!!

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Uncle Benzz · #6 05-19-2021, 11:57 PM

My 3.5 603.971 pulls to 4500 rpm and shifts nice and firm. It needs a timing adjustment seems a tad rich at idle...

Quote:

Originally Posted by Diseasel300

Yes, the IP will give the same power output regardless of whether you have it on a 603 or 606. The injection quantity is the same, so the power output will be the same. Horsepower increase comes from additional fuel and timing. The difference between the 3.0 and 3.4 pumps is largely in the torque capsule and RPM limiting. The 3.0 pump will pull hard to ~4600 RPM before tapering off fuel while the 3.4L pump will fall on its face ~4K with the 3.0L engine. It's just how they're tuned for the different displacements.

The bottom end on the 60x engines is extremely durable. If there's no noise or symptoms of wear, leave well enough alone.

Felching · #7 05-20-2021, 10:09 AM

Quote:

Originally Posted by Uncle Benzz

It needs a timing adjustment seems a tad rich at idle...

Diesels by definition can't be "rich" at idle. If its smoking, thats incomplete combustion or oil consumption.

Diseasel300 · #8 05-20-2021, 10:19 AM

Quote:

Originally Posted by Uncle Benzz

My 3.5 603.971 pulls to 4500 rpm and shifts nice and firm. It needs a timing adjustment seems a tad rich at idle...

Your fuel cut is at ~4500 RPM. Yes, the engine will run up to that point, but it's way down on power due to the IP tapering fuel starting at 4100 RPM.

Quote:

Originally Posted by Felching

Diesels by definition can't be "rich" at idle. If its smoking, thats incomplete combustion or oil consumption.

Probably the oil crossover port in the head starting to leak into #1 or clapped out valve guide seals.

rwd4evr · #9 05-28-2021, 02:29 AM

So I can adjust the torque capsule and all the internal bits with it out of the car same as a om617 pump correct? Rack limiter? Is it a mw pump as well? I can't recall right now.

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Felching · #10 05-28-2021, 02:51 AM

If you don't know those basic facts of your pump, you should definitely NOT be messing around inside of it. A wrong adjustment could make it undrivable or even destroy the engine.

Uncle Benzz · #11 06-15-2021, 10:44 AM

She pulls nice to 4500 no sign of fueling tapering .. In fact It gives a small plume of black coal there.. She's torqued very nicely. I like the 3.5 for that reason. Moves the tank nicely.

Quote:

Originally Posted by Diseasel300

Your fuel cut is at ~4500 RPM. Yes, the engine will run up to that point, but it's way down on power due to the IP tapering fuel starting at 4100 RPM.

Probably the oil crossover port in the head starting to leak into #1 or clapped out valve guide seals.

Diseasel300 · #12 06-15-2021, 11:05 AM

Quote:

Originally Posted by Uncle Benzz

She pulls nice to 4500 no sign of fueling tapering .. In fact It gives a small plume of black coal there.. She's torqued very nicely. I like the 3.5 for that reason. Moves the tank nicely.

I don't really care what you think you know about how your car runs, having tuned a couple of these pumps now and going by the published data on how they are tuned from the factory, they taper fuel starting at 4100 and cut at 4500. Not here to argue with you. When you fix your rough idle and loping issues that you don't listen to anyone else about (and have been posting on and off about for 2+ years), come back and let us know how much of an expert you are.

Uncle Benzz · #13 06-15-2021, 11:35 AM

You are Feeling like douche canoe today? I get it.. Lot's of acid makes you that way..

Careful with the accusations genius.

Quote:

Originally Posted by Diseasel300

I don't really care what you think you know about how your car runs, having tuned a couple of these pumps now and going by the published data on how they are tuned from the factory, they taper fuel starting at 4100 and cut at 4500. Not here to argue with you. When you fix your rough idle and loping issues that you don't listen to anyone else about (and have been posting on and off about for 2+ years), come back and let us know how much of an expert you are.

Diseasel300 · #14 06-15-2021, 12:21 PM

Quote:

Originally Posted by Uncle Benzz

You are Feeling like douche canoe today? I get it.. Lot's of acid makes you that way..

Careful with the accusations genius.

Lack of facts got sand in your vag? Still waiting to hear how the timing being off can make your diesel run "rich". You haven't contributed any useful data or advice to this thread.