My guess and it is only a guess. If you find the fuel milage still acceptable and you are not blowing a lot of smoke especially on acceleration. I might leave it off.

Inversly if the milage is poor and too much smoke it is realy best to fix it properly. I know the last sentance is kind of excessive.

In combination with this issue it may pay you to examine the base pressure in the injection pump. Only if there is no smoke and milage has not declined below common averages for your model.

Just in case the pressure it is very low and it is taking the removal of the alda to make the car driveable. It is probably unlikely but it is past time to get some of the more common issues nailed down better.

They may have been circumvented too long or are not issues. In fact in my mind checking the available fuel pressure in the injection pump base is almost as important as checking the valves on the older models. There will be noticeable effects from sub standard pressure. A lot of them performance related.

I also have no ideal of the percentage of vehicles that have low pressure. The car in most cases will still drive okay but not perform overall as it should usually. This is now absolutly proven for rational purposes and not pie in the sky. A lot will test normal and a lot will not. If nothing else it will give a massive boost to your knowledge of the fuel system.

This message is not particularily aimed at the gentleman with the newer diesel. Yet since he uses wvo it could be an issue as well. The required pressure gauge is about ten dollars.

If the pressure is low and you restore the pressure to 19 lbs. Consider it the best return on ten dollars spent you ever got. If the pressure is normal you then know it is for sure. Leaving the gauge permanently installed is another consideration as well. There are many benifits.

Anyways it is nice to know the thread starter has got his car running much better with the end in site.

Weellll, the end may be farther away than we thought. With the car seemingly running well, packed up the kids, dog, and loaded up the roof rack and drove 7 hours for a family reunion. Car did fine, a little slow on the hills, getting 23 MPG going through the mountains, then seemed to lose power in the last 10 miles of the trip, and would stall everytime I stopped from there on out. I just let it sit for a few days, then test drove it, and it seemed fine, again.

BUT, on the way home, I had much less power, and in the middle of West Virginia, it slowed to a stop. No amount of fiddling could get it running again (changed filters, even the tank screen), and had to get towed the rest of the way home. First time I've ever had to get towed. Ever.

In an effort to resist my urge to set the thing on fire, I parked it out back for a while, and am just now getting back to it. I've been tempted to just put it on E-bay and let someone else fool with it, but I have a hard time giving up.

So, it now starts, and can move under its own power, but is idling rough. I swapped in another lift pump, as it really seems like a fuel starvation problem (and since I had a spare sitting around), but that didn't make any real difference.

Picking back up on this thread, I dusted off my fuel pressure testing kit, and lo and behold, I'm only getting 6 psi in the line just before the IP. I pinched the return line, and got the pressure up to about 20 psi, and it seem to help marginally (maybe just wishful thinking).

In any event, now that I know I have fuel pressure problems, and having read some other threads on that issue, I'm thinking perhaps the relief valve (or in Bosch-speak, the "overflow valve") in the IP has failed.

Any thoughts?


Patrick Skelley
Bedford, Virginia
1970 Unimog 406
1972 350SL 4.5
1972 300SEL 6.3
1978 240GD
1979 300GD
1987 300TD

Reading only your last post, I suggest to remove the plug on the #1 exhaust runner (it's gonna be loud!). If performance improves, the oxidation catalyst by the transmission might be clogged. Also try pinching the return line to the fuel tank. The IP check valve can stick open allowing fuel to bypass the delivery valves. This latter event shouldn't affect mpg, though.

Sixto
87 300D

Check your gas tank vent is not clogged. Loosen gas cap and hopefully no vaccum

Wow.this is turning into a quite a "How to troubleshoot anything thread". Good luck skelly. Hope you find out what it is. Your putting so much work into this. Did u run grease on your last trip? I m guessing your not until u get this thing straight. Good idea. Thanks for Keeping us posted.

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What Would Rudolph Do?
1975 300D, 1975 240D, 1985 300SD, 1997 300D, 2005 E320 , 2006 Toyota Prius