Replaced plastic lines on 606, still sucking air! - Page 2 - PeachParts Mercedes-Benz Forum

TMAllison · #16 09-19-2007, 06:26 PM

Cal - The pumps dont go bad unless someone screws with them in my opinion.

There is a shop in the Bay Area that many dealers use to rebuild/repair them. Replacements (rebuilts) supposedly run about $1k.

I've got the info at home if you have to go that route. I for one would do the K40 and the check valve first.

patbob · #17 09-19-2007, 06:33 PM

Sucks in air within seconds of shutting the car off? Is the fuel system under a vacuum or something? Like maybe the tank vent is plugged?

Mister Byrnzoil · #18 09-19-2007, 06:43 PM

Yeah, I'm thinking blocked tank vent or blocked tank screen. causing xtra pump 'suck'.

Consider putting one of those clear inline filters at various points between your tank and ip to see if they accumulate air. this should rule out everything 'cept the ip itself.

Do you/have you ever run wvo/vo/homebrew BD?

muleears · #19 09-19-2007, 08:15 PM

Never any BD but did run some blended WVO (50/50) a couple weeks ago. What is in it now is about 90% pump diesel and 10% WVO. Could this have damaged the pump? Its the same stuff I've been running my 87 on for the last year and a half. Obviously if this is the problem, no more WVO...

nhdoc · #20 09-20-2007, 07:04 AM

Quote:

Originally Posted by muleears

TM, No delay at shutdown at all and no CEL or codes. Mech. called this afternoon to tell me it is either the check valve at the banjo on the back of the IP or the fuel pump. I'm sure the checkvalve isn't too expensive (relatively speaking) but he tells me the fuel pump is $1300

Rusty and Phil don't list them but I'm getting a price. Any additional input is appreciated.

IIRC that checkvalve is actually built into the banjo bolt and only costs a couple of dollars and is easy enough to change once the IM is off so it is worth a shot though I don't see how it could cause air to leak into the system if it had failed. Did you say they replaced the o-ring on that bolt already? That's what I'd be suspect of first.

I don't see how it could be the injector pump itself (that's apparently the part they are quoting $1300 for, must be a rebuilt).

If air is being drawn into the fuel system there must be a leak somewhere. I think if it were me I'd probably try disconnecting the fuel feed and return lines, plugging the return and lightly pressurize the feed line with compressed air...say just a few PSI and look for leaks. You could spray down every joint with soapy water and look for bubbles...then I would think you'd find the source of the leak.

Although I would not run WVO in this car I don't think that using 50/50 once could cause this problem. I also like the idea of checking the tank screen to make sure it is not causing the lift pump to pull too much vacuum...

muleears · #21 09-20-2007, 08:30 AM

nhdoc, they told me they replaced ALL the O rings, I did not ask specificaly about that one. I did ask if he meant the IP for the $1300 and he said no it was the fuel pump. They said they hooked it up to the smoke machine to look for leaks, I assume that would be about the same as a few PSI and the soapy water you mentioned. We have not (to my knowledge) checked the tank screen. The banjo/check valve is being overnighted and hopefuly will be here early enough today to be installed. I will post when I have anything more. Thanks for the help so far.

nhdoc · #22 09-20-2007, 10:20 AM

Quote:

Originally Posted by muleears

nhdoc, they told me they replaced ALL the O rings, I did not ask specificaly about that one. I did ask if he meant the IP for the $1300 and he said no it was the fuel pump. They said they hooked it up to the smoke machine to look for leaks, I assume that would be about the same as a few PSI and the soapy water you mentioned. We have not (to my knowledge) checked the tank screen. The banjo/check valve is being overnighted and hopefuly will be here early enough today to be installed. I will post when I have anything more. Thanks for the help so far.

If they are replacing the banjo bolt make sure they put a new o-ring and 2 new crush washers on it when the install the new one. Common sense would dictate they would without having to be told so but lots of techs lack common sense.

If they are quoting $1300 for that little lift pump then I'd probably start looking for another shop. I haven't priced it specifically but I'd be shocked if the list price on it exceeded even 10-20% of what they quoted. It's nothing more than a mechanical plunger arrangement bolted to the side of the IP...

muleears · #23 09-21-2007, 04:51 PM

Well... they replaced the banjo/check valve, I hope using new O rings and washers, and it didn't make any difference. They won't be looking at it again until monday and I know they are going to tell me I need an IP. Is it just possible that they are right?

nhdoc · #24 09-21-2007, 06:16 PM

Quote:

Originally Posted by muleears

Well... they replaced the banjo/check valve, I hope using new O rings and washers, and it didn't make any difference. They won't be looking at it again until monday and I know they are going to tell me I need an IP. Is it just possible that they are right?

I'd get a second opinion before committing to a 4 digit repair like that. Why not bring it to the dealership shop and see what they think? I just don't know how the IP could be letting air into the fuel system after shutdown without it leaking like crazy while it is running. I think you need a more experienced tech to look it over...while this isn't rocket science sometimes simple things are overlooked because of inexperience.

muleears · #25 09-22-2007, 08:20 PM

Could a bad IP exhibit these symptoms?

TMAllison · #26 09-22-2007, 09:46 PM

I'd be more inclined to suspect the computer.

I agree with Marty, time to visit the dealer before proceeding further. Talk to the service manager and get yourself assigned to an advisor who has the best diesel mech in HIS group on techs.

pberku · #27 09-22-2007, 11:05 PM

While parked on a level ground, see if it makes a difference to your starting problem wether your fuel tank is almost empty or almost full. If it does make a difference, then the problem is indeed likely fuel/air leak related. If not, then time to look elsewhere.

Specifically what you want to look for is if its better with the fuel tank full, and worse with the fuel tank almost empty?

muleears · #28 09-23-2007, 06:00 AM

If it is better full, does that mean I have a fuel pump problem?

pberku · #29 09-23-2007, 11:59 AM

Quote:

Originally Posted by muleears

If it is better full, does that mean I have a fuel pump problem?

Not necessarily, but more likely it will mean that the higher level of the fuel in the tank will cause the fuel to leak out versus a lower level of fuel, which in turn will allow air to leak in.

TMAllison · #30 09-23-2007, 12:42 PM

Cal - I've re-read your entire thread. I believe you've repalced every oring except for the S/O valve now and have confirmed the integrity of the tank and feed lines using smoke?

If you're of a mind to keep after this yourself I would continue look at the following:

1) S/O valve oring and/or valve. Is possible the oring has a bad seal which only shows up when warm under conditions of expansion. Is possible for valve body to develop hairline cracks and also for valve to become sticky or pokey closing that only shows up under conditions of expansion.
2) New pre-filter. Is possible your's has a bad seal or crack which only shows up under conditions of expansion.
3) New fuel filter. Is possible your's has a bad seal which only shows up under conditions of expansion.
4) New oring at fuel filter bolt. Is possible yours got pinched.
5) K40 relay. Signal to S/O valve may be partially interrupted at shutdown preventing valve from closing compelety.

Regarding your previous questions about the DV's: I've never seen air leak into the fuel system there, only fuel leaking out.

2, 3 & 4 are cheap and easy to do.
5 is easy to do. Costs ~$80.
1 is pretty easy to do by reaching under the IM. I can do it in under 30 minutes. Oring is cheap, S/O valve is ~$165.