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View Full Version : Uncharted territory: inside the injection pump


mortskeg
18-02-2005, 02:46 PM
<center>http://img.photobucket.com/albums/v400/glen_ekstrom/injpump.jpg</center>
Until recently I have had a pretty good idea about the different mechanical processes of my diesel engine with the exception of one very important component- the injection pump. I knew that it was responsible for sucking fuel all the way from my tank to the engine compartment, and then delivering a high-pressure shot of fuel to each cylendar at the appropriate time, but the exact inner-workings remained a mystery to me. However, in repsonse to Glen's 81 engine trouble, Dr. Cool was so kind to post this awesome link- an online vw Diesel engine manual. (http://www.fostertruck.com/Files/VW_diesel_77-83.pdf)
The manual does a great job of getting into the simple theory behind the engine and dives deep into the injection pump with illustrations I've never seen in any bentley. However, my question goes beyond what I've been able to get out of this publication or the rest of the web- and may be answered by someone who has had the nutz to tear into a bosch injection pump for whatever reason.
I have been thinking a little bit about building an "appleseed" biodiesel reactor in order to keep my chemestry knowledge up to par (can't be outdone by all the meth-heads now can I?). I have read conflicting reports about what all you need to change on the fuel system, but if I go forward with the biodiesel, would like to change all the small rubber fuel hose that goes from the tank to the steel lines, and then from the steel lines to the filter/ pump return to a compatable material (viton). But since my injection pump seems to work pretty well I don't have much interest in taking it in to be rebuilt, and was trying to figure out where all the "incompatable" seals are at inside the pump.
In looking over the manual, I couldn't really tell where rubber seals would be used inside the pump as it all looks like closely machined parts. I see the low-pressure side utilizes a rotary vane pump, but I was guessing that the vanes were just chunks of metal that float in the channels in the rotor.
Anyhow, if any of you have any idea where any seals are inside the pump, or what detriment would be caused to the pump by using properly prepared biodiesel, please let me know. Also I have on my list of future things that I could do to the pickup "if I were a rich man" a NA 1.9d engine swap. I was wondering if the 1.9 pump that came with these new engines had "compatable" seals already. This might be a good question for the dark lord of the sith, since he just had his 1.6td pump rebuilt.
So that is my question. Where are these mystery seals/orings/gaskets or whatever. I don't put alot of miles on my pickup like I used to but I thought that it might be fun to try and make my own fuel and "stick it to the man". Plus I'm down with the environment and lowering emissions- but at 3.45/ gal- commercial biodiesel can take a long walk- IMHO.[:p] Ha ha.

Darth Garry
18-02-2005, 06:25 PM
When I had my pump rebuilt they gave me a "body bag" of a completely disassembled pump. I'll look through the hundreds of parts and see if I see any rubber seals. It's not scientific, but a start. I'll also ask the guy who rebuilt it when I see him next time.

Garry

mortskeg
18-02-2005, 11:47 PM
You truly are the man. In a good way. Not the "stick it to the man" man. You know.

Diesel
19-02-2005, 07:49 AM
The thing with biodiesel is, it likes to plump and melt rubber. That's bad on exposed low pressure, exposed fuel lines. Inside an injector pump, it's not that bad. The bio will expand the o-rings and make them fit all the more snugly, actually stopping small leaks. However, if and when you take said pump apart, you will have no hope of getting those seals back into their now confined space. That's not a problem, because if you are taking one apart, you must be rebuilding it! There are some o-rings around the main shaft that spins and goes in and out, if I'm not mistaken (don't take my word for it, though,) and a couple more here and there. I wouldn't worry about it. I have a bunch of diesel stuff and have been running various percentages of biodiesel in all of them with no ill effects.

Darth Garry
21-02-2005, 12:11 AM
Awesome Diesel!

Morts, I checked my "body bag" but things are so completely disassembled I couldn't make much sense of it. There are literally hundreds of parts floating around in there, I kind of looked at it for a minute and scratched my head and knew that someone like Isaac would set the record straight.

Garry

mortskeg
23-02-2005, 02:06 PM
Awesome guys. I may start experimenting with this stuff sometime down the road. I guess I should see if I can find a car in the wreckers (newer) with compatable fuel hose as buying new 1/2" ID bulk viton is nearly $20/ foot! (http://www.greaseworks.org/viton_bulk) Maybe viton can handle liquid kryptonite or something.

Diesel
24-02-2005, 12:13 AM
Viton shouldn't be that expensive. I've seen $6-7 per foot range. McMaster has it by the foot, I think. Fill Rite pumps are now equiped with viton seals and hoses for complete compatiblity with biodiesel and the various alcohol blends for gas engines. Pretty cool.

Diesel
24-02-2005, 12:16 AM
That's www.mcmaster.com. They have all kinds of cool industrial stuff. The cataloge is like a dictionary.

mortskeg
24-02-2005, 04:15 AM
Sweet, thanks!

mGunter
18-06-2006, 04:08 AM
hey, if you live near any coast especially, but maybe marine supply places in general, may as well check out the boat store.my local biodiesel place sells viton
for 6-7 bucks but it's only 2-3 a foot for barrier lined Trident brand marine grade diesel fuel line at the fisheries supply house. same stuff. oh, but try no to act like you're getting a great deal...they also have bio-cide to prevent the bacterial build-up in yr fuel system for way cheaper.

mortskeg
18-06-2006, 10:47 AM
mGunter, welcome to the forum!

Good advice, I've always thought the viton was a bit on the spendy side, and have used urethane in my pickup, though the Trident line would probably be an even better alternative. Here's a list of thier distributers for those interested-

http://www.tridentmarine.com/stage/purchase.htm

Thanks again for the tip. :cheers:

Asymtave
19-06-2006, 07:03 PM
I was indeed crazy enough to rebuild (relative term) my pump last winter. It was leaking out the drive shaft seal. This seal is an oil seal - metal body with a rubber seal that it backed up by a fine spring to "squeeze" it to the input shaft.

The reason the seal failed is because the drive shaft bushings were worn out either from high miles or from excessive cam belt tension. Unfortunately, in order to get at these busings the pump has to come entirely apart. (FYI - these bushings have to be carefully installed and reamed ON THE CENTERLINE OF THE PUMP. This requires a specialized jig that I obviously don't have. I had the fuel injection shop do this.)

On to the seals. The seals are either O-rings, molded rubber or the oil seal I mentioned above. From what I've read, bio-diesel (or the alcohol in it - especially home-brew) will eat conventional rubber. Also from what I've read, manufacturers switched to synthetic rubbers in the early 90's that will withstand the bio-diesel. So - you have the oil seal at the driveshaft input, a molded rubber seal between the governor cover and the main pump body, and various O-rings. Some of these are: between the cast iron pump head and aluminum body, around the cold start lever shaft, under the cover this shaft goes thru, under the cover directly opposite the cold start lever, around the fuel control lever input shaft (a bushing here also), around the internal fuel pressure regulator, around the "max fuel" screw, and probably some others.

People have found ways to change most of these with the pump in the car, even the one between the pump head and pump body. The one that can't be is the input drive shaft seal. People have devised ways of pulling this seal out and replacing it without disassembling the pump, but it's tough to do without trashing the shaft.

I think all new seal kits are bio-diesel safe. Maybe buy one and keep it on hand and replace seals when and if they fail. Avoid taking this pump apart at all costs as long as it's running. I consider myself lucky (not smart or talented) that I got it back together and working without help.

Eric

mGunter
21-06-2006, 11:04 PM
awesome. wondering about rebuilding a pump lately. been jacking around trying to get this little truck to stop pulling air into my lines for MONTHS. pulled the tank, cleaned the screen, blew out the lines, changed all hoses, filters, injectors, checked unions, bled the crap out of it too many times. it all started when my wife (who's the only one physically able to comfortably drive the truck) ran it out of fuel. next couple times it was driven, it would run for about 5 minutes before it'd get to bucking, bogging, stallin out at idle and generally run like crap. i'd look at the clear line from filter to pump and there were huge 4" long bubbles headed for the pump. figuring they're coming from the back end, or before the filter i started eliminating all possible entrances i.e. hose clamps, fuel filter, pulled the filler cap thinking maybe there was a vaccuum, tightened up the filter again, checked all the hoses again, changd everything that maybe was leaky or old, all the while takin the truck out for spins of about 5 minutes and gettin the same air in the line. lookin at it while its running, i noticed that if i throttle it up after it's run awhile and let off quick, the bubbles actually travel backwards FROM the pump to the filter. get it? like when there's been immense fuel pressure forward in the line and it abruptly stops when throttled back, there's all this air pulled in, travelling UP the tube to the filter, where i think it sits til you trottle up again when it's then pulled back down to the pump, and gets all weak and clunky. thought i had this whipped last weekend with cleaning out the tank and screen, drove it 30-45 minutes and then about 30 minutes the next day no trouble, but my wife took it up this beaast of a hill ( denny in seattle) and by the top it was crappin out and sprayin fuel all over the timing belt. not a hose and i'm afraid its the front shaft seal. ran it a couple more times after cleaning it up just to make sure and it takes like 5 minutes for the leak to start. guess it has to heat up. sound familiar..?. guess this was pretty longwinded, but its been drivin me to drink/keepin me up at night. anybody care to weigh in on this?

Asymtave
25-06-2006, 02:02 AM
That's more or less how mine started. After sitting there would be air in the line from the filter to pump. It would start hard, and after running a while the air would purge or clear out. I never ran it hard I guess, so once I was going I was OK. I was getting ready to put a check valve in at the filter or maybe a assist pump back at the tank when the seal got to bad it was throwing diesel everywhere.

This all occured within a few hundred miles. Rebuilding the pump took a lot of time and luck, and I still had to pay the fuel injection shop to do some things. I did it more or less for the learning experience. If you can get a rebuild for $350 that's a bargain.

Eric

P.S. Maybe running it dry was it for the seal on the input shaft - ie. the seal needs the fuel for lubrication.