lots of gas in oil

[megachrome]

Good day!

I have a 74 450SLC with 130K miles. In general it runs well, and is in wonderful condition. However, in the three years that I have owned it, it always smelled as if it was leaking gas. I found leaks in the rubber hoses to the guel rail and fixed them, but they would start to leak again in a few weeks.

Recently, my wife could not start the car. It would try to catch, but clouds of acrid white/blue smoke would pour out of the exhaust and it would die.
After sending it off to the mechanics, he found that the oil level was high, and the oil was contaminated with gas. He turned down the pressure of the fuel pump, changed the oil / spark plugs and cold start valve.

After a week, it is beginning to exhibit the same symptoms. The oil smells like gas, and it may not start after it has been recently turned off.

Looking for other opinions of what may cause this type of issue, as it does not seem to be related to fuel pressure or a bad cold start valve.

Many thanks!
Dan

[Tomguy]

1) Running too rich
2) Leaky injectors spit gas down into the engine while it's shut off
3) Leaking CSV makes you run too rich or leaks while it's shut off

The cause of gas in the oil is almost definitely one of these 3. Check your CO %, it should be no higher than 2%! Any more means you're way too rich. Around 1% is ideal for power and efficiency. You COULD have a pressure too high at the rails, but I doubt it. It should be around 29-30 PSI.

[megachrome]

Thank you Tom,

1) Running too rich
I was running rich, my mechanic adjusted the mix, and I don't feel this would be a problem anymore.

2) Leaky injectors spit gas down into the engine while it's shut off
This is a god possibility, but how does one test for it other than replace the injectors?

3) Leaking CSV makes you run too rich or leaks while it's shut off
The CSV was replaced. it's possible that the rnew part is as bad as the one it replaced, but injector leakage would seem more probable.


Many thanks for your input!

Dan

[Tomguy]

There are a few ways to see if they leak w/the engine off...
- One is to put a pressure gauge on the line. There should be 30PSI (give or take) at the rails overnight. Hell, I think mine probably still has 30PSI at the rails, and it's been at least a month since I fired it.
- One is to pull the injectors out of the heads (while still on the rails) and put a newspaper below them. If the paper gets wet, they leak.

Oh, and I forgot to ask: How did your mech adjust the mixture? Did he use a CO meter? He NEEDS to. Use a CO gauge to set running mixture (med revs under load meaning engine revving with tranny in drive). 0.5-2%. Then after running mixture is set, set the idle mixture to the same % using the idle mix screw on the ECU.

If neither of these were done correctly, you'll still be too rich.

[megachrome]

Thanks Tom,

I suspect that I will probably have a go at this myself.
I will pick up a pressure guage, and run the overnight test to see where I go from there.

If it leaks, I will test the individual injectors, and replace as needed.
BTW, these seem to be fairly expensive little buggers. In looking around, I have found them for as little as $159, but see reconditioned injectors for $25.

Any experience with the quality of the reconditioned units?

Many thanks!
Dan

[Tomguy]

Originally Posted by megachrome

In looking around, I have found them for as little as $159, but see reconditioned injectors for $25.

Are you KIDDING me? These used to be $60 a pop! Guess a lot of people are finding value in the D-Je 4.5's, and inflating part prices!

I had 3 leaky injectors myself. I soaked all 8 in a mixture of carb cleaner and acetone for 2 days, and activated the injectors a few times a day. Cleared out the injectors, and stopped the leaking!

[megachrome]

Hello Tom,

Well, it's Saturday, and I ran out this morning and picked up a Fuel pressure gauge and 8 seal kits.

I checked the oil this morning, and found that the level had rasied 1/4" since last week, and it reeked of gas again.

I set up the pressure gauge in the connection between the two fuel rails and fired it up. I was reading 22 PSI. When I turned the engine off, it went to 0 immediately. I then called my mechanic to see what he had to say, and he tells me that my model (450 SLC) does not have a check valve on the pump, and it should go to 0 PSI when turned off. He asked me to block the line to my cold start valve, and check the oil agian in a few days.

I'm now going to drain off a few quarts of oil, and top it off to monitor the level with the CSV blanked.

Now I'm stuck, without a pressurized system, I can't really think of a way to check whether or not the injectors are leaking.

Any more ideas?

Thanks!
Dan

[Tomguy]

1) Something's wrong with your adjustment or you have seriously leaking injectors. You should have at LEAST 27 PSI when running
2) I'm pretty sure ALL D-Jet pumps have a check valve. Someone can correct me if I'm wrong.

[megachrome]

OK, it's Saturday again.

Here is where I stand:

Last week I replaced half the oil, and carefully measured the level on the dipstick. I also plugged the fuel supply to the cold start valve to remove it from the equation.

This morning I pulled my car into the same place where I measured the oil last week, and it was again up a quarter of an inch. This is the same gain that I have been having, approx a quarter of an inch of fuel each week in the sump.

I then pulled 1 bank of the fuel injectors, unplugged the electrical connectors, and placed them on newspaper. After running the car for 30 seconds, I checked the newspaper and it's bone dry.

Same for the other side with the same results.

Here is what I know:
1. It's not the cold start valve.
2. Unless I'm missing something, it's not my fuel injectors.

Here is what I dont know:
How else can gas get in the oil at this rate?
The car gets driven about 20 miles a week. My wife drives it 1 mile each way to work, and shopping on the weekend.

Any ideas gleefully accepted!

[Matt L]

The engine runs with half of the injectors missing? That should not happen.

Does the pressure regulator on this engine connect to the intake manifold?

[alabbasi]

I'm very familiar with this problem. My car is a 73 280SEL 4.5 with the same D-Jetronic injections system. The car would run fine and then suddenly the computer would tell it to run super rich and it would run like crap. This would leave gas in the oil. Over time the car would get harder an harder to start. I disconnected the trigger points at one time and cranked the car. When it fired, it took split the muffler wide open.

I got a computer from the junk yard and replaced mine and it's been running fine since.

I would be skeptical that the leaky fuel injectors would leave so much fuel in the oil. it should only leak whatever is in the fuel rail which should not be a lot. Now everytime I see a D-Jet computer at a junk yard, I grab it.

[megachrome]

Hello Matt,

Oddly enough it did. I was surprised as well.
It seemed to cycle 1 second on and one second off as if each bank recieved fuel in opposing cycles. I know it shoudn't, but it did!

The pressure regulator connects to the fuel rail.

Thanks!
Dan

[megachrome]

Hello alabbasi,

I guess I am at a point where I would need to suspect the electronic control unit (Computer?).
However, the car runs fine, all of the time. I can not characterise it as overly rich at this point. But if I gather enough evidence that this may be the case, you may have to fight me for a spare unit!

Many thanks!
Dan

[Tomguy]

Originally Posted by Matt L

The engine runs with half of the injectors missing? That should not happen.

My 4.5 has run on 3 before. I've never tried 2 but I wouldnt be surprised if it did.

If it isn't leaky injectors either your idle mixture IS too rich, your running mixture IS too rich, or your TPS is maladjusted and, when fuel should be nearly cut off during deceleration, it isn't, and gas is pouring in at 2k RPMs when the throttle plate is closed (no air to burn it).

[Mark DiSilvestro]

Originally Posted by megachrome

Here is what I dont know:
How else can gas get in the oil at this rate?
The car gets driven about 20 miles a week. My wife drives it 1 mile each way to work, and shopping on the weekend.

Any ideas gleefully accepted!

The fact that the car only is driven 1 MILE each way to work, and is never warmed up enough to get off of the cold-rich mixture, could be part of your gas-oil dilution problem.

Happy Motoring, Mark