Problem bleeding bosch fuel injector pump

[jrchafin]

Hello all, have a Mahindra 7520 with 700 hrs on it, about 6 years old.

Using it the other day and I noticed a diesel fuel smell, found a leaky gasket in the bosch injector pump. The leak was on a gasket underneath a plate that was facing the engine block, so I had to take the pump off to fix the gasket. I have no idea why this started leaking, but it was running fine otherwise.

I removed the pump, and replaced the gasket as well at the other gaskets involved in the removal. I reinstalled it, and cracked the line that enters the pump, running through the filters and hand pump to the top of the injector pump. I hand pumped until fuel came to this point and then re tightened that line.

I knew the pump wasn't bled completely, but decided to try and start it. I cranked it and it ran great. put it at full throttle for a minute or so, no problems, no leak. I shut it down thinking I was done.

The next day it wouldn't run at all, just cranks and cranks with the starter, a little grey smoke coming from the exhaust. I figured I was air locked, so I removed the high pressure lines and tried to hand pump fuel through the pump. I have pumped that thing probably 50 times or more, and it feels like it's pumping, I can hear a hiss, but no fuel comes out of the high pressure ports.

What am I missing?

Thanks in advance.

 

[Winmac]

You must crank the engine over to get fuel out of the high pressure side, the hand pump only fills the body of the pump, when you open the bleed screws.

 

[Raised on a Deere]

You must crank the engine over to get fuel out of the high pressure side, the hand pump only fills the body of the pump, when you open the bleed screws.

Not sure if your system is self bleeding or not but even after filling the pump with the hand pump you may need to crack the injector fitting loose to allow air to escape while you are cranking the engine. Open just a "smidge" and close immediately as the engine starts running. It will smooth out quickly after a rough sputtering start. Just be careful to not get you hands in the path of squirting fuel. It is under very high pressure. I place a rag around the wrench that is spanning the fitting and tighten immediately as the engine sputters. Hope this helps

 

[jrchafin]

Thanks guys. Got it running, and this time it promptly started leaking again. :-( Now I have to figure out what is wrong with this pump. Seems it is building up excessive pressure and blowing this gasket out.

 

[Raised on a Deere]

Thanks guys. Got it running, and this time it promptly started leaking again. :-( Now I have to figure out what is wrong with this pump. Seems it is building up excessive pressure and blowing this gasket out.

I have a Dexta (3 cyl perkins) that the pump started leaking and while trying to find a fix, I attached a made up metal container held in place with baling wire and let it catch fuel. Emptied it into tank two or three times a day. That temporary fix became the permanent as that is the way she still sits. Don use that tractor much any more. No power steering and no spring in seat, no loader, -- What good is it??:laughing: But for about ten years that is the way I kept my place mowed.

 

[jrchafin]

Anybody else have this problem? I don't want to just replace the gasket only to find that it blew out because of something wrong with the pump and do more damage. Maybe it's building up excessive pressure? I shouldn't just have a gasket failure on such a new pump without another cause. I've heard some say it's the new diesel fuels.

 

[Winmac]

Can you describe which gasket was changed, I'm not sure from your earlier description which it is. Picture might go a long way.

Pressure in the body is regulated around 70-90 psi max, but it could over pressurized if there are issues. I'd be tempted to replace the gasket again, did u use oem? Often they are special material

 

[jrchafin]

Good idea Winmac. Its the shiny plate at the bottom in the pic labeled Y330. This is the right side of the pump as it sits in the tractor, against the engine block.

 

[jrchafin]

My pump is a bosch VE type pump. Found this article that shows a larger version of the same basic pump, and it apparently has a max fuel pressure of 17,400PSI! I don't know if I'm getting that much pressure, but that would explain a lot, the special gasket, blowing out a regular gasket in no time, 1/4" grade 8 steel cover plate.
Injection System Basics - Diesel Power Magazine

 

[skyhook]

Sounds like you need a pump rebuild.

 

[Winmac]

That fuel under the cover would never see those high pressures the article mentions.
What was there for a gasket, I'm thinking there are orings but it's been awhile since I had one apart.

A rebuild would be the last resort unless you have several hundred dollars to spare.

 

[jrchafin]

Agree on the rebuild. Going to replace the gasket and see how it goes. The gasket is definitely a specialized one. Looking online, many pumps have an O-ring sealing this, and it looks like they also fail frequently. The guy at the injection pump service told me that the newer models have this specialized gasket. It is a stamped piece of metal coated with a tough, flexible rubber type material. It looks like the rubber coating disintegrated on the old one which is what caused it to leak.
If it lasts another 6 years I'll be fine with that. If it fails quickly, I'll have the pump rebuilt. Just need a day off from work so I have time to reinstall everything.

 

[JimRB]

If you send me a note I can send you a few Bosch manuals that explain VE pumps.

 

[JimRB]

Or do some Google searches. Bosch VE diesel fuel-injection pump manual. - 4x4 Community Forum

 

[jrchafin]

Thanks for the manual link. It gives a decent overview of what's going on in the pump. Couldn't find PSI in that chamber though. That's OK. I have a new gasket and we shall see if it works.

 

[jrchafin]

So finally got time to put the new gasket in my fuel pump and re-install. It doesn't leak any more, but unfortunately doesn't run right either. I think there may be something wrong with the pump, but before I take it for a rebuild, I want to make sure I'm not missing something I can fix.

It's a VE type injection pump, which runs off a pump gear with a woodruff key. I did not crank the engine or move the location of the pump gear while the pump was off, and did not rotate the pump either. I was careful to align the key with the pump gear when I put the pump back on, and I've aligned the timing marks between the pump housing and the engine block. The engine runs, but very rough and has some strange behavior.

It starts and idles fairly well, but when I give it fuel, it doesn't do anything at first. Then, once I add enough throttle, the engine takes off and jumps up RPM, running fairly well, but still rough. It smokes gray intermittently, and even back fires some.

Controlling the throttle on the pump itself with my hand, the first inch or so of rotation doesn't have any effect in the engine, and then it suddenly takes off, jumping to 2000RPM or so. If I release the throttle it returns to a rough idle. So is something stuck inside the pump? I can't see any other explanation for why the throttle would be doing this.

Any advice on troubleshooting would be much appreciated.

 

[adietrich1214]

I just had same problem with my 6530 mahindra. 2000$ later after a pump rebuild found that these bosch pumps REALLY suck.
299 hrs and basically a common issue is for there timing piston to fail and go out of normal movement range. this lets it chew itself and the entire timing apparatus , hitting the outer plate and causing the gasket to finally fail. This is the piston that runs perpendicular to the engine just under that gasket plate on the inner side of the pump. Ernie at D&W diesel in Syracuse knew exactly what it would be and was able to describe to me exactly symptoms and what the plate would look like.
Not a mahindra part but really lousy for a 3500-4000$ part.
Apparently this timing piston and circuit are very hard to bleed so if pump goes dry even once, there can be air that doesn't leave and results in the timing piston rattling to auto destruction. You get smoke and failure to reach rpm above 1400-1500 as well as loss of power.
I'd suggest not fooling around with the inner gasket and get it in to a reputable pump shop ASAP.
On the 6530 and I suspect other mahindras, be careful removing pump. easy to crack the timing cover(we did and fortunately had a talented welder who could weld the mediocre cast material around there pump shaft access plate) to do it again Id go straight to removing the timing cover and gain proper access. hope this helps someone.
I will be contacting Bosch.....

 

[thepumpguysc]

NO NEED to contact Bosch.. They have already determined the cause & there is a service bulletin that states the reason..
Dirty filters & or air in the system.. NO WARRANTY..
I've seen pumps that were replaced w/ 20 hrs on them, destroyed internally.. because the customer didn't change the filters.
Another good preventive measure is> replace the lift pump, if so equipped..
I've rebuilt hundreds of those pumps for the same reason..
Air gets in the system, starts hammering away at the advance piston.. the small clip becomes dislodged & eats the internal aluminum housing to bits..
The first symptom is loss of power, hard start & then leaking pump at the advance plate..
I cant count how many calls I get for>> "do you carry the gasket that goes on the little plate at the bottom of a Bosch pump??"
a $3.00 gasket usually turns into a $2000.00 pump.. The main pump housing ALONE is $500.00 list price.

 

[adietrich1214]

Right but to make a pump that touchy and reportedly difficult to bleed the advance piston seems ridiculous. Getting rid of this machine. All maintenance was followed per manual.