Author Topic: Backfire and not running well (Read 12798 times)

w113bkk · « **on:** January 31, 2016, 19:42:27 »

Prior to my ownership of my 230sl it had been sitting for about 2 years with marvel mystery oil in the cylinders. Recently I put fresh gas in the tank and started it up. I can get it to idle if I hold my foot about 1/4 of the way on the throttle. It will run but will backfire every 15 or 20 sec. If I take my foot off the gas the car will eventually putter and the engine will stop.

I was going to go pull the plugs and clean them off. Does anyone else have ideas on things to check.

Tyler S · « **Reply #1 on:** January 31, 2016, 19:52:43 »

Does it run better when its cold or hot? You may want to check that the WRD (warm-up or warm running device) isn't stuck. If it seems like it is running extremely rich, check the CSV (Cold Start Valve) and make sure it isn't leaking, It could have become stuck in its bore the first time you went to start it. Also check for vacuum leaks.

Benz Dr. · « **Reply #2 on:** February 01, 2016, 07:21:17 »

Our cars will not run with fouled spark plugs. The engine will start but it won't stay running and it will stall under a slight load like putting an auto into gear.

This does sound a lot like WRD problems though.

ja17 · « **Reply #3 on:** February 02, 2016, 14:33:28 »

Yes, start with the cheap easy things first (spark plugs).

w113bkk · « **Reply #4 on:** February 07, 2016, 20:47:44 »

I'll give it a try

w113bkk · « **Reply #5 on:** February 24, 2016, 01:08:49 »

I worked on the car last night with my friend. All 6 plugs were drenched in gas and looked identical. I cleaned them and re gapped them. We checked the timing and points. Everything looked fine. The cold start solenoid was getting power. My friend tried to disconnect it to see if it made a difference in how the car ran and it did not change things. He tried adjusting the fuel injection pump with the screw at the rear of the pump. We checked the fuel filter and things looked good.

Next we intend to check fuel pressure and check the dwell of the points.

Tyler S · « **Reply #6 on:** February 24, 2016, 02:09:36 »

The cold start valve can still leak even with no power to it. It should only have power to it while cranking. The needle and seat can become corroded and stick open. Remove the small 7mm hex screw on the side of the CSV. Turn the key to on position, do not start it. There should be no fuel coming from the opening. If there is the CSV is leaking internally.

ja17 · « **Reply #7 on:** February 24, 2016, 15:41:32 »

Start with a new set of plugs next time. Fouled ones don't always clean up right. Its nice to rule the plugs out with-out a doubt. A good investment for $20.00 and you can always use the old ones if they are truly good. The injection pump rack can also be stuck. It is easy to check this. search up the information, it should be easy to find.

Tyler S · « **Reply #8 on:** February 24, 2016, 19:20:09 »

Quote

The injection pump rack can also be stuck

Joe, I was thinking the same thing. It's severely over fueled. Stuck rack, stuck open cold start valve, or plugged return. Possibilities are probably in that order. The fact it clears up with throttle input, adding air to match the overfuel.

Benz Dr. · « **Reply #9 on:** February 24, 2016, 23:37:33 »

Quote from: Tyler S. on February 24, 2016, 19:20:09

Joe, I was thinking the same thing. It's severely over fueled. Stuck rack, stuck open cold start valve, or plugged return. Possibilities are probably in that order. The fact it clears up with throttle input, adding air to match the overfuel.

I think we should move the new kid to the head of the class.

Peter van Es · « **Reply #10 on:** February 25, 2016, 20:48:57 »

If you like I can activate the Karma feature of the website… then we can all up vote or down vote each others contributions

w113bkk · « **Reply #11 on:** March 02, 2016, 04:25:23 »

Here is an update on things that have been checked and things I plan to check next as the car still won't idle smoothly or run right.
1) checked cold start as described and everything worked properly
2) checked IP rack , moved freely
3) checked volume of gas with line disconnected and that was fine
4) drained gas
5) changed plugs
6) checked check valve and cleaned out
7) removed #6 spark plug wire to check spark and car seemed to run the same as it did when it was connected as if it is currently running on 3 or 4 cylinders

Next up I intend on taking the injectors off to check them at my friends shop.

Any other ideas for this anomaly?

ja17 · « **Reply #12 on:** March 02, 2016, 05:04:17 »

You might also try loosening each injector line (at the injector) one at a time with engine running, to see if fuel immerges and if the engine changes.

Tyler S · « **Reply #13 on:** March 02, 2016, 06:49:35 »

Quote

checked check valve and cleaned out
7) removed #6 spark plug wire to check spark and car seemed to run the same as it did when it was connected as if it is currently running on 3 or 4 cylinders

So it seems you have multiple cylinders that are misfiring. Do that same test to every cylinder to isolate which ones aren't firing. Make sure you have a good strong spark at each plug. Have you checked the points/dwell yet?

jameshoward · « **Reply #14 on:** March 02, 2016, 11:38:50 »

Have you checked the resistance of your plug leads and ends to ensure they're correct and functional (do a search around resistance, plugs and leads - there's a ton of info about this on the site)? Probably wouldn't account for intermittent running, but it's one more thing to rule out. Points and dwell are an easy and early check.

Pinder · « **Reply #15 on:** March 02, 2016, 13:17:14 »

Another thing to try is swap the injector on #6 with one of the cylinders that work to see if its injector is the issue or not.

If all the spark plugs were fouled I would think your getting fuel but maybe not well atomized. Try taking the injectors out and clean them with carb cleaner or lacquer thinner. Soak them for several days. try using a cheap ultrasound cleaner. Also try blowing compressed air through them. Its possible to gently lift the tip of the valve on the injectros while pressure feeding cleaner through it. (wear googles). If you have a pop tester use that.

Tyler S · « **Reply #16 on:** March 02, 2016, 17:07:07 »

What did the old fuel that you drained look and smell like. If it was really bad it could have varnished in the injectors , IP, and return line. Both could cause thngs to stick. The varnish will usually occur at the top of the fuel level or anywhere it is in contact with air. If the Ignition system is sorted out, start looking at fuel related components (ie plugged return line, injectors leaking etc.)

w113bkk · « **Reply #17 on:** March 05, 2016, 21:43:33 »

I put about 5 gallons of 93 octane with some marvel mystery oil into the tank prior to trying to start it. There may have been some old gas in the tank. When I drained the tank the gas was yellow colored. I'm not sure if it is just discolored because of the marvel mystery oil or from some old gas being in there and mixing with the new gas.

I haven't checked resistance on the spark plug wires. I have checked the points but have not checked the dwell.

I intend on taking the injectors out and bench testing them and cleaning them at my friend's shop.

w113bkk · « **Reply #18 on:** July 04, 2016, 02:07:54 »

We have yet to figure out why my car won't run right. Today we adjusted the valves, put in a new condenser and ballast resistor and a fresh set of Bosch plugs. The only options in my mind at this point are the coil or that the injection pump is not timed properly. Any thoughts?

Cees Klumper · « **Reply #19 on:** July 04, 2016, 05:40:20 »

If the car ran properly before it was put away, that should rule out the injection pump timing. Yes, check the coil and ballast resistor. Also check the throttle linkages for play, although that's a long shot. Can't really think of anything else, besides all the things already mentioned. Did you end up cleaning the injectors?

ja17 · « **Reply #20 on:** July 04, 2016, 05:48:14 »

Check to see that the WRD is not stuck. Then check to make sure the rack is not stuck.

w113bkk · « **Reply #21 on:** July 04, 2016, 16:46:35 »

I replaced the injectors. The rack isn't stuck. My friend who worked on the car did get it running but did not see the car for 6 years. I'm not sure if anyone else touched it or possibly fooled around with the pump. I did a compression test as well and the car has good compression.

What should I check with the WRD?

Tyler S · « **Reply #22 on:** July 04, 2016, 16:58:06 »

You may want to back out the Idle Air screw on the intake manifold a substantial amount and try to get the engine to idle first. This will introduce more air and counter the extra fuel. Then chase the cause of the over fueling.

w113bkk · « **Reply #23 on:** July 05, 2016, 16:24:55 »

I have a feeling something is going on with the pump. I am going to crack the fuel line for the cylinders the plugs had carbon or nothing to see if I am getting fuel. I will then check to see if the pump is 180 out.

badali · « **Reply #24 on:** July 05, 2016, 17:25:08 »

I just finished reading the entire post and I think the points could still be the problem. When I first started my car this year it stalled while I was on the phone and I did not shut off the key right away and burnt the points. The car had similar symptoms as what you described initially. I could not see the burn mark on the points until I removed them. If the car was running fine before there are now a lot of things that could be messed up with improper adjustments.

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Author Topic: Backfire and not running well (Read 12798 times)

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