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Tractor Talk Discussion Forum

Electronic to Mechanical Pump

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bm3501466

04-03-2006 18:17:12




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I have heard that the mechanical injection pumps placed on the GM 6.5 diesels for military use are a lot better than the electrical pumps for civilian use during 1994. How difficult is it to exchange an electrical injection pump with a mechanical one? What all would be involved in doing this?




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Bob

04-03-2006 19:31:30




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 Re: Electronic to Mechanical Pump in reply to bm3501466, 04-03-2006 18:17:12  
Does the truck have an automatic transmission?

If so, it needs the PCM that controls the injection pump to control the tranny. If the 'puter doesn't "see" the injection pump anymore, it's going to get pretty weird. It will likely go into "limp home mode", and refuse to shift up over about second gear.

If you have $$$$, you can buy a stand-alone tranny controller to operate the tranny, however.

Also, you would have to change to the older-style glow plug controller, as the 1994 controller is only a relay, operated by the PCM.

That being said, I have a 1994 with the electronic 4L80E tranny. I have owned it since it had about 54,000 miles on it, now it has 190,000.

I have replaced the Fuel Solenoid Driver ONCE in the years I've owned it. I moved it to a home-made remote mounted heat sink, and have never had trouble with it again.

I'm sure the injection pump WAS replaced before I got it, however, I've never had to touch it. So not all are bad. Actually, due to some real horror stories of folks throwing $$$$$$ at one of these trucks because the dealership did not know what was wrong, and attempted to fix it by throwing $$$$$$ parts at it, the system has gotten a worse "rap" than it really deserved, at least in most cases. MANY injection pumps were scrapped, some under warrantee, some not, because of simple things that could have been repaired, not involving actual replacement of the pump.

If you wiring harness and connectors are in good shape, the electric lift pump is good, and you have a decent injection pump and mount the PMD on a good heatsink (the module then becomes the FSD), the system should work well for you.

I have had quite a number of vehicles with the mechanical pumps, and the electronic system is hands-down better for cold weather starting (injection timing advance control is better), and, also mileage is better with the electronic system.

If your vehicle is fixed by a shop that knows what they are doing, or you become a member of the Diesel Page, and learn to troubleshoot and repair the truck yourself, there's no reason it shouldn't give good service for a long time without to many repairs.

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jdemaris

04-04-2006 06:04:15




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 Re: Electronic to Mechanical Pump in reply to Bob, 04-03-2006 19:31:30  
A few agreements and disagreements with what you stated. In reference to many pumps and other parts being changed when not necessary - that's absolutely true and it also applies to the older GM diesels dating back to 82. I've seen many complete engines get condemned and removed when there was nothing wrong with them. I'm still driving a few. In slight defense of GM though, when they first started having the problems with the Stanadyne/Roosamaster DS4 fuel systems - dealers were doing complete replacements on the recommendation of Stanadyne. Seems, at first, Stanadyne did not know how to fix the system they created. In regard to the electronic system providing better fuel mileage and cold-starting, I've seen little evidence of that. With cold-starting - what HAS happened is more consistent quality-control throughout. With the older diesels - car, truck, and farm tractor - there was a wide set of tolerances - plus or minus that applied to many individual parts or systems on engines. So, it was a crap-shoot. I've got two 82 GM 6.2 diesels and an 85 Ford 6.9 diesel that start amazingly well when cold - absolutely as good if not better than any new truck on the market. I've also got an 83, 87, and 91 that have been poor starters since new. John Deere had the same problems with inconsistency up to their 50 series of Ag. tractors. And - fuel mileage? I've got an 82 1/2 ton 4WD that gets 24 MPG on the highway, and an 83 2WD that gets 26 MPG. My neighbor recently tried to upgrade from his 91 Dodge 3/4 ton 4WD with 5.9 Cummins - that gets a consistent 18 MPG on the highway. He just bought a new GM 3/4 ton 4WD with the Japanese Power-Max diesel and the best he can get is 14 MPG on the same highway trip. My 94 Ford 3/4 ton 4WD turbo 7.3 IDI gets 21 MPG on the same trip (all mechanical injection). And with lighter vehicles? Jeep now has a turbo-2.8L diesel in their Liberty and fuel mileage is not impressive for a vehicle that small at 26 MPG. I had an 86 Isuzu Trooper 4WD with an Isuzu turbo-diesel and it consistently got 30 MPG on the highway - and no electronics. My wife's 91 Volkswagen Jetta diesel gets a consistent 51 MPG on the highway. My son has a 2003 Jetta diesel with electronic controls that gets 45 MPG. I'm not saying that there aren't any newer diesel trucks with decent mileage - but on the average - there is NO benefit in fuel-mileage or cold-starting because of the electronic emmisions-based controls.

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RodInNS

04-04-2006 10:56:58




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 Re: Electronic to Mechanical Pump in reply to jdemaris, 04-04-2006 06:04:15  
I would disagree with you about ease of starting on electronic engines vs mechanical engines. I'll use Cummins as an example. I've got an old NTC855-350 + that winds and winds when trying to start it. Mind you, the compression isn't what it used to be. But if it's below freezing, you need not think of starting it, unless it's been on life support for several hours. I've also got an N14-435, again with lots of miles, that will start at -15C without a hitch, unassisted. It literally turns twice, and it's running. It starts better cold than warm.... which doesn't make a lot of sense, but it does. I think most of the difference between the 2 could be attributed to timing advance, so I think it makes a considerable difference. I would say there is also some fuel savings with electronic controls, but it's a bit harder to quantify. The controls are likely more accurate, and as you say, consistent, which allows a smaller engine to be pushed to higher specs with less chance of harm. There are definite efficiency gains from pushing 400 hp from and 11 L engine over a 14 L engine. I would certainly argue that heavy trucks, by and large, are a good deal more efficient than 15 years ago. Pickups are not likely any better, if as good, but look at the power they have today. 15 years ago, they didn't come with a 3-1/4 cummins under the hood. Your wife's Jetta is much the same game. It's a lighter, less powerful car than your son's TDI. That added to the fact that your son probably doesn't drive like your wife.... At least I don't drive the Jetta like my mother does... She would easily see 25-30% better mileage than me, because my right foot knows one position... sitting on the floor boards. Not that this has anything to do with the original chevy question....

Rod

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jdemaris

04-04-2006 11:32:44




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 Re: Electronic to Mechanical Pump in reply to RodInNS, 04-04-2006 10:56:58  
I can't speak from personal experience with the Cummins engines - I don't own any. Just know a few people that do. But, I doubt the differences in starting have anything to do with timing. That would not make sense. Electric or mechanical, establishing optimum static timing for starting purposes is easy to do. With many pumps with slotted mounts where they bolt, you can just rotate the pump housing to advance static timing. Deere Company had us doing it ad nauseum with many poor starting diesels that came out with the 40 series ag. tractors. Ultimately, it made no - or very little difference. Our Volkswagen had a timing-advance control by the steering column - for cold starting. Again, with the Cummins - I don't know if all the older engines were poor starters, or just some. With the GM 6.2 and 6.5s, some are great starters, and some lousy - and it has nothing to do with timing, fuel delivery amount or glow-plug timing. It's all in the basic fundementals of engine assembly - e.g. how high the piston standout is above block-deck, combustion chamber size in the piston, valve head recess, etc. My 82 Chevy 6.2 will start when it's 20 degrees F with little effort. My 83 will barely start at 60 degrees F without some jerking around and excess glow-plugging. Both run great, once running. My 85 Ford with the IH 6.9 is the best of the bunch, and I've started it a few times at 0 degrees without plugging in the heater and it fires right up (after the glow plugs cycle). In regard to my wife's 91 Jetta as compared to my son's - it's not the driving habits that make the difference - we've used his car - and he's used ours. He bought his after being impressed with our little junker. We borrowed his to see if we liked it better. His does have a little more power, and handles better, but it's hardly noticeable. I read through a lot of Volkswagen technical data for their newer designs - and the main thing that has happened is - they are trying to "dumb down" diesels for Americans - and make them start, sound, and run like gas engines. At the same time, they also have to meet more stringent emissions requirements. That is why the mileage is not as good with the newer ones in the US. Overseas it's different. Many comparible diesel cars get much better fuel mileage in Europe. As I understand it, General Motors gave up on their 6.5 diesel because it became to costly to keep up with emission's standards without sacrificing fuel mileage and reliability. So, they dropped it, and let Isuzu make their Powermax diesel instead. It is likely that newer diesels are more consistent in their manufacturing processes - so you don't find some that start well and others that don't (unless something goes wrong). Also, just by the nature of design, a direct-injected diesel if built right will be a better (or faster) starter than an IDI down to a certain temperature. Below that cold thresh-hold, an IDI with properly working glow-plugs will outstart the DI engine - not counting the use of block-heaters.

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RodInNS

04-04-2006 15:17:47




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 Re: Electronic to Mechanical Pump in reply to jdemaris, 04-04-2006 11:32:44  
The new Cummins system is fully electronic, with electronic unit injectors. The old PT systems had mechanically activated/timed, pressure/orifice metered injectors. The new systems simply have a crank position sensor feeding the brain box, and that tells the injectors when to jump. So it allows for variable fuel timing, as far as I'm aware. The old NTC's were notoriously known as hard cold starters. I think it's fairly well accepted that electronics smartened up the starting on most Cummins and Detroit engines.
As far as the Jetta's go, I think some people's mileage will vary. I know one guy who's getting I would say probably mid to high 50's (mpg US). He was getting the advertised 64 miles per Imperial gallon, which is somewhat larger than yours, and I haven't done the exact conversion. This was from an '03 Jetta TDI. My mother has an '04 Jetta TDI, and it's probably doing low-mid 50's (US), but I've had it down to low 30's on some low level flights (80 mph). It can certainly burn fuel on a hard pull. I think most of the decrease that some people see is basically just dragging a bit more car around than the old models. New jetta's are a bit heavier than the old boxes. There is no theoretical reason for an IDI engine to be more efficient than a DI engine. You are quite correct though, that the new emissions requirements for Tier III, including EGR will decrease a diesel's mileage. I haven't looked at the specs on that lately, but I seem to recall it as being quite significant. for what it's worth...

Rod

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jdemaris

04-04-2006 20:08:02




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 Re: Electronic to Mechanical Pump in reply to RodInNS, 04-04-2006 15:17:47  
Forgetting people's driving habits for a minute, or anecdotal fuel milage reports - all you have to do it check the EPA ratings. They might not represent real-world driving conditions, but they work well for comparing vehicles with each other for a given year, or looking at a spectrum of years - at>Link

They>Link do not test heavy pickups, however, only up to 1/2 ton trucks. With the Cummins engines, and common-rail injection - if that's what they are using, I still doubt that it accounts for the better starting - I'm sure there are other factors involveed. Common-rail with electronic controls works well to control emissions and "diesel rattle" along with flame-travel in the combustion chamber. In regard to the diesel "rattle", I'd prefer to keep it, I like it. I have noticed recently that many companies that have used Cummins power for years in their trucks are swithing to the new 5 cylinder Damlier-Mercedes diesel. Not sure why, but they're popping up all over the place. On the general subject of old diesels versus modern - a few remarks were made here about the old Deere 4020 versus a newer 6300. Mr.Buick-Deere claims the fuel savings alone with the modern tractor would offset the purchase price. I checked Nebraska test ratings for both tractors - and at some speed and horsepower ratings - the 4020 is more fuel efficient that the much newer 6300. And, one of most fuel efficient diesels ever tested at Nebraska is the Deere two cylinder diesel - and also the Japanese "Deere" 1650.

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Mike M

04-04-2006 07:03:37




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 Re: Electronic to Mechanical Pump in reply to jdemaris, 04-04-2006 06:04:15  
That 82 1/2 ton 4x4 what gear ratio and tranny do you have ? Does turning up the pump help you get those very high MPG figures ? I had heard that it did help.



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jdemaris

04-04-2006 07:19:32




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 Re: Electronic to Mechanical Pump in reply to Mike M, 04-04-2006 07:03:37  
Turning the pump up has no effect on fuel mileage except - if you turn it too high - you'll get unburned fuel, black smoke, excessive heat, and lower mileage.
If you turn the pump up, and at the same time, find a way to use the extra fuel - like turbocharging, at least then you'll be getting extra power for the extra fuel use. My 82 1/2 ton 4WD has a rare option package - at least I see it described that way whenever I see another one for sale anywhere. It has an aluminum four-speed manual trans - Muncie I think - and fourth gear is an overdrive. It's more of a car-type transmission, kind of looks similar to what's in my 65 SS Chevelle. It does NOT have a granny low-gear. The engine turns 1800 RPM at 65 miles per hour. If this was a 2WD, it could be a problem because of the high gearing. But, since it's 4WD, it has the dual-range transfer case that gives it a nice low range when needed. For many diesel pickups, RPMs is everthing. Fuel efficiencly goes down very fast with higer speeds. With some trucks, mileage of 22 MPG at 65 goes down of 15 MPG at 75.

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buickanddeere

04-04-2006 13:40:23




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 Re: Electronic to Mechanical Pump in reply to jdemaris, 04-04-2006 07:19:32  
Driving at 75MPH requires 1.33 times the power to overcome wind resistance than 65mph. Other additional drivetrain loses add up to yes indeed, dropping the mileage from 22 to 15. Some of the older mechanical era engines also used a simple egr valve if there was one used at all. If the egr is eliminated combustion efficiency is improved.



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jdemarisj

04-04-2006 20:15:31




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 Re: Electronic to Mechanical Pump in reply to buickanddeere, 04-04-2006 13:40:23  
I've got several with, and several without the EGR valve. On the diesels, it doesn't do very much. On a same year GM, a standard-duty diesel came with one, and a heavy-duty came without it. Often the one without the EGR gets worse mileage - but that's becasue once labeled "heavy duty" GM could turn the fuel up a bit and make some smoke - and get away with it. I've never noticed much difference between them in performance or mileage. In regard to the extra power and wind-resistance at higher speeds, of course that's true. But in addition, most diesels have a narrow efficiency band, much more narrow than for most gas engines. So, the extra RPMs outside of that efficiency curve help create a large fuel-mileage drop.

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Mike M

04-04-2006 09:24:25




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 Re: Electronic to Mechanical Pump in reply to jdemaris, 04-04-2006 07:19:32  
That manual tranny must be the key ? I had an automatic 700R4 with a 3.08 rear end and only got 19-20 on my 6.2 and if you pulled even a small trailer it really dropped.



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jdemaris

04-04-2006 09:38:41




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 Re: Electronic to Mechanical Pump in reply to Mike M, 04-04-2006 09:24:25  
I've got an 86 K5 Blazer with the 6.2 diesel and 700R4 trans. and it can get a best of 21 MPG on a flat highway, and averages 16 MPG. It actually gained close to 1 MPG on the average when I unplugged the wire harness from the trans. so the lock-up converter was eliminated. By unhooking it, the engine labors much less and drives much nicer. But, I live in a hilly area with very little flat driving. I assume that if I lived in flatland, the lock-up and overdrive would give better mileage instead of worse.

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jdemaris

04-03-2006 18:44:37




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 Re: Electronic to Mechanical Pump in reply to bm3501466, 04-03-2006 18:17:12  
I've done a few but it's been awhile. Yes, the mechancial DB2 pump is MUCH better, cheaper to buy, cheaper to work on, more reliable, etc. But, some states don't allow the change because of emmissions laws. Here in NY, no one seems to care or notice. The only major component you need is the mechancial DB2 pump and they're easy to find. That's what the Chevy 6.2s and early 6.5s use in civilian use, and with the military, they kept the system for everything, also the Ford-IH 6.9s and 7.3s (the Ford pumps won't fit a Chevy). I've got a bucket full of DB2s. The pump off a 6.2 is fine, but the fuel should be turned up a little. Some HD trucks that have the three-speed T-400 automatic trans. might need a VRV valve attached to the pump. If you don't have one already, then you don't need it. It simulates changes in engine vacuum by sensing moviement on the injection-pump throttle linkage - but I think it's only uses with the T-400 trans. VRV stands for Vacuum - Regulating - Valve.

The guy that owns the 6.2-6.5 diesel website has an article that gives all the details you need. The following is the link to his site - just cut and paste. I think his site is not all free anymore - but if you email him, he might send you the info. Also, at the bottom of this message is the "blurb" from an ad that runs almost constantly on Ebay where the plans are for sale. If you cut and paste that link, you'll pull up an old Ebay ad and you can contact the guy if needed.

Link

Electronic Fuel Injection to Mechanical Fuel Injection Part II
By Jim Bigley
Why switch from EFI to MFI? The answer is simple; injection system replacement cost. This article completes what was stated last year by giving you the final pieces of the puzzle for converting your 1994 or newer 6.5 diesel to mechanical fuel injection.

From the Ebay seller:
The DB2 Conversion Guide is a new book that provides all the information needed to successfully convert a Stanadyne DS4 electronic fuel injected Chevrolet or GMC 6.5L Turbo Diesel to a reliable DB2 mechanical fuel injection. It includes a complete parts listing (with GM part numbers), list of suppliers and where to source low-cost and easy to find parts necessary for the conversion. In addition to the text, there are detailed full color pictures and wiring charts. The Guide covers all affected components including throttle pedal, turbo wastegate, automatic transmission operation and cruise control.
Volume 1.0 covers 1994 - 1995 2WD trucks with 4L80E automatic transmission and 1994 - 1995 2 and 4WD with manual transmissions. It has information pertinent to other models of trucks, but not specific instructions.

The DB2 Conversion Guide will also show you how to eliminate these other troublesome components: Vacuum pump & related hoses Vacuum Turbo Boost Canister Electronic Throttle Pedal (APP) Boost pressure & IAT sensors
Link to Ebay: Link

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