Injection pump settings

[69280sl]

My mechanic, who I believe is very knowledgeable about pagodas, tells me my IP is pretty worn and should be rebuilt. He sends them to Pacific.

In the meantime, he tells me my choices are:
1) Set the pump for the best possible idle and running. The mixture will be rich and the plugs will foul and require frequent changing, or,
2) Set the pump leaner, plug life will be enhanced but the car will run rougher, particularly at idle.

Does this make sense?

Any other suggestions/comments?

Thanks
Gus - 280sl

[rwmastel]

quote:Originally posted by 69280sl

My mechanic tells me my IP is pretty worn and should be rebuilt. He sends them to Pacific.

Gus,

First, Pacific is a fine place to send a pump for a rebuild, one of the 3 or so places recommended by owners on this forum.

Second, did he say why he came to this conclusion?

Third, what is the history of your car?
 - Does it have high milage (200,000+ miles)?
 - Did it sit not running for years?
 - I'm looking for obvious reason for the fuel pump to need the rebuild...

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[69280sl]

Hi Rodd:

My car was running badly. He sorted it out, said (among other things that the IP rack was sticking), said the "IP was maxed out",with the settings he made on it. Ran fine initially, but the plugs fouled within 200 miles to the point that the car was missing and running badly. I brought it back to him today and got the information I listed in my previous post.

The car probably has 178,000 miles, altho there is a slight chance it may be 78,000.

It was last registered in Florida as the winter car of a gentleman with residences in Florida and Chicago. It is possible that it sat unused during the summer months.

As I said, I believe the mechanic is very knowledeable about pagodas, (by way of example, he rebuilds older auto trans. for the MB dealers in the area) but I don't know that what he recommends is always in my best interest.

Gus -280sl

[hands_aus]

I wonder what your mechanic means by IP was 'maxed out'

When I bought my car the fuel mix could not be 'leaned out' but after I did the things below my car went from giving me 9mpg to now giving me 18.5mpg around town. All this without an inj pump rebuild.

Things i did with advice and guidance from this group.....

replace the inj pump thermostat,
remove a few shims under the warm running device,
adjust all the linkages to be correct lengths with no play,
make sure the venturi valve is closed at idle,
make sure the electrical side of the engine and cold start system was working correctly
make sure the cold start valve is not leaking fuel even when it is not activated ( if this valve leaks more than 3 drops a minute MB recommends reseating the valve) it will also make it impossible to lean out the inj pump and hence your plugs will foul.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[69280sl]

Thanks for your information Bob, I will take the steps you suggest.
The first thing I will check is leaking at the CSV.
I didn't ask at the time, but by "maxed out" I assume he could not lean the mixture further, consistant with good running.

Thanks again
Gus
280 sl

[Benz Dr.]

The idle mixture setting really doesn't affect the setings at road speed. This is set at the back of the pump on a test stand during calibration. If the pump runs rich at idle and can't be leaned out the whole pump will very likely be rich but this is more a condition caused by wear or some other mechanical part that is not set or working right.


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 SL Barn
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