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1973 450 SL - D-Jet - NoCat - Smell Fuel When Cold

1K views 7 replies 5 participants last post by  Fonzi 
#1 ·
Please don't waste too much time on this post. I'm again just fishing for ideas from all you more experienced fellas.

I've got new injector seals and know I need to install them ASAP. However, I thought I'd ask if there are other immediate things to check (off the top of your SL-info-full heads).

I personally think my car is running fairly well when warm, but think maybe I have a few issues at the cooler startup temps. For example, I drove about 3-5 miles to a gas station on the highway before starting my fuel consumption test drive. Sure I smashed the gas pedal and hit nearly 100 mph to just test how the car was driving, but I swear I could see the needle dropping from just under 3/4 of a tank down to a little above a half tank (maybe 5/8ths a tank realistically). But on my test to see how good of fuel economy I could possibly get, the needle never left full on my 40 mile, ~2500 rpm, 60-65 mph ride, for which I calculated 16 mpg (no brakes whole ride). BUT the car was warmed up for that ride. Also, I nearly always smell fuel when I first start up the car. It stinks up my garage really badly if I back in. If I just start the car, pull out and pull back in, and shit the car off, the garage stinks. Also, with lots of driving of that type, and just a few blocks here and there, I think I'm getting 5-7 mpg.

So I think the car running too rich at cool temperatures. (Vacuum leak at my injector seals maybe?) Maybe there's nothing that changes except the unspent fuel burns off in the hot exhaust when the car is warm.

Just looking for ideas.

You guys know I'm a serious novice, and haven't really checked the points, or analyzed my exhaust, or even pulled the spark plugs yet.

Right now, injector seals are the only item on my project list. I'm wondering if there are other items I should add.

THANKS!
MIKE
 
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#5 ·
I assume that this post here by MBGraham is the post that shows how to install and AFR gauge. http://www.benzworld.org/forums/r-c107-sl-slc-class/1547632-cool-hell-gauge.html#post4379674 If you follow the link in that post, it appears MBGraham shows how his 1972 performs with the DJet and how the fuel mix gets leaner after the car warms up a bit.

So that all makes me feel better, knowing that a well tuned car probably runs about the same way as mine. However, you are right. The only way to really know if it's running the same way is to have some real-time numbers from an AFR.

Now I also know what AFR stands for: Air Fuel Ratio meter. :) I learn something every day around here!
 
#7 ·
You really shouldn't have a fuel smell, ideally. I would check all the hoses under the hood: fuel rails to injectors, pressure regulator to fuel rails, left to right rail, fule laril to cold start injector, and to / from charcoal cannister. In short: everything! Then check the fuel lines underneath the car at the back. To/from the tank and pump, then forward.

I had a bunch of old bad lines that leaked until I replaced them. The smell went away after that. Until the fuel pump went and started leaking.

Just check everything, and replace anything that looks old or worn. The job is not that bad if you start with a nearly empty tank and do it outside with a bit of a breeze.

Just remember that you need to get Fuel injection system tubing, it's designed to deal with the pressure of a fuel injection system. That is important!!

The peace of mind is valuable. You know that it's not going to go up in flames on you.

Scott
 
#8 ·
Thanks Scott. I think you've hit on something that I quickly dismissed when I didn't see any leaks.

That really was my first thought. When I thought I smelled fuel I opened the hood and checked the rails and injectors immediately. I couldn't find any leaks whatsoever. I dismissed it. I probably should not have. I'll be sure to keep a keen eye out.

Since I've had them before, I now know what to look for. I also understand that they can leak, stop leaking, and leak again. They don't need to necessarily keep leaking once they've started, but will surely leak again.

I'll add fuel hose to the list! :)
 
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