89 300E:F.Injector Leak/Flooding At Startup - PeachParts Mercedes-Benz Forum

joel · #1 04-04-2006, 09:37 PM

I am beginning to suspect that my car has leaky fuel injector/s. At start ups, whether hot or cold, it starts rough and seems like fuel is flooding for several seconds then it clears up. Engine idles rough and misses.

It might be related or not but this car will not start at first attempt to start. Maybe second or sometimes third.

Any ideas how to isolate leaky injector?

Mike Murrell · #2 04-05-2006, 12:25 PM

Joel:

What condition is your ignition system in?

Distributor cap, rotor, spark plug wire suppressor caps; spark plugs.

Without knowing any history, I'd first wonder about the ign. system since this problems occurs both hot & cold.

joel · #3 04-05-2006, 12:42 PM

Quote:

Originally Posted by Mike Murrell

Joel:

What condition is your ignition system in?

Distributor cap, rotor, spark plug wire suppressor caps; spark plugs.

Without knowing any history, I'd first wonder about the ign. system since this problems occurs both hot & cold.

Just had them all replaced. My indy also suspected the injector/s since this car failed emission testing on idle with high HC reading.

Mike Murrell · #4 04-05-2006, 12:57 PM

Joel:

I may stand corrected, but I believe high HC is indicative of a rich condition. If so, there could be issues other than tired fuel injectors.

Did your tech test the functionailty of the EHA? I believe it handles the leaning/enrichment process as per feedback from other parts of the system.

Moneypit SEL · #5 04-05-2006, 01:45 PM

HC = unburnt fuel. High HC does not necessarily = too rich. A lean misfire can also cause high HC. Until you determine the cause of your rough idle, it's just guessing.

lkchris · #6 04-05-2006, 01:46 PM

You can inspect your sparkplugs to identify a rich cylinder.

If your mileage is pretty high, probably best to replace all injectors. It's not too difficult on M103, and injectors are only $36 ea. You need new seals and probably plastic mounts, too.

mctwin2kman · #7 04-05-2006, 03:42 PM

I once had these same exact issues. First off do not just throw money at the thing by replacing all the injectors. I did just that only to find out that it was not the injectors.

What you need to do is either you test it or have the indie test or check the following.

First check every vacuum rubber connector and replace all that look bad, just replace them all if you want peace of mind. Then check all the rubber hoses that connect the IACV to the intake. If they are not soft and plyable then replace them. Next check the intake boot that connect the AFM to the throttle body. Next check the AFM is set up properly for Basic/Zero Position. Then check the mixture to make sure it is correct. Also test the O2 if you have not yet. Next verify that your plug wires fall into the proper range. I went through two full sets of wires and 3 sets of just the end connectors before I gave up on Bosch and Beru junk wires that were not even close to the spec out of the box. I finally found NGK Premium and they tested spot on out of the box at 987Ohms. Spec is 1KOhm with a useable range of 800Ohms to 1.3KOhms according to MB specs. My Bosch tested at 1.2KOhms cold and the Beru at 1.1KOhms cold, when hot they both were over the 1.3KOhm spec.

And last check the Engine Water Temp Sensor. It is what tells the CIS-E controller the engine temp so that you get proper enrichment when cold and proper cold start valve operation and IACV and EHA operation. When that goes it cause hard cold starts and hard warm starts but mostly normal other operation. Basically if it is bad the Cold Start Valve will not actuate and the IACV and EHA will not provide enrichment and increased idle at cold start time. So you would not get the engine to fire on a cold start and stay running without needing to give it gas or restart and then it would run but stumble due to lack of enrichment and increase idle. Once warmed up enough everything would smooth out. Same somewhat for warm restarts, except you would have to keep cranking to get it to restart and then once it did it has to burn all the extra fuel dumped in before it stabalizes.

So you can start with that temp sensor if you want then move onto all the other stuff to save time.

joel · #8 04-05-2006, 10:05 PM

Quote:

Originally Posted by Mike Murrell

Joel:

I may stand corrected, but I believe high HC is indicative of a rich condition. If so, there could be issues other than tired fuel injectors.

Did your tech test the functionailty of the EHA? I believe it handles the leaning/enrichment process as per feedback from other parts of the system.

Mike, what are the values of a working EHA? I've read something about twitching it, too?

joel · #9 04-05-2006, 10:10 PM

Quote:

Originally Posted by Moneypit SEL

HC = unburnt fuel. High HC does not necessarily = too rich. A lean misfire can also cause high HC. Until you determine the cause of your rough idle, it's just guessing.

This is actually what my indy told me, unburnt fuel, which is what he suspects to be leaky injectors. In fact, the CE light comes on and off when I step on the gas generously.

joel · #10 04-05-2006, 10:14 PM

Quote:

Originally Posted by lkchris

You can inspect your sparkplugs to identify a rich cylinder.

If your mileage is pretty high, probably best to replace all injectors. It's not too difficult on M103, and injectors are only $36 ea. You need new seals and probably plastic mounts, too.

What do a expect to see from the spark plug?

joel · #11 04-05-2006, 10:18 PM

Quote:

Originally Posted by mctwin2kman

I once had these same exact issues. First off do not just throw money at the thing by replacing all the injectors. I did just that only to find out that it was not the injectors.

What you need to do is either you test it or have the indie test or check the following.

First check every vacuum rubber connector and replace all that look bad, just replace them all if you want peace of mind. Then check all the rubber hoses that connect the IACV to the intake. If they are not soft and plyable then replace them. Next check the intake boot that connect the AFM to the throttle body. Next check the AFM is set up properly for Basic/Zero Position. Then check the mixture to make sure it is correct. Also test the O2 if you have not yet. Next verify that your plug wires fall into the proper range. I went through two full sets of wires and 3 sets of just the end connectors before I gave up on Bosch and Beru junk wires that were not even close to the spec out of the box. I finally found NGK Premium and they tested spot on out of the box at 987Ohms. Spec is 1KOhm with a useable range of 800Ohms to 1.3KOhms according to MB specs. My Bosch tested at 1.2KOhms cold and the Beru at 1.1KOhms cold, when hot they both were over the 1.3KOhm spec.

And last check the Engine Water Temp Sensor. It is what tells the CIS-E controller the engine temp so that you get proper enrichment when cold and proper cold start valve operation and IACV and EHA operation. When that goes it cause hard cold starts and hard warm starts but mostly normal other operation. Basically if it is bad the Cold Start Valve will not actuate and the IACV and EHA will not provide enrichment and increased idle at cold start time. So you would not get the engine to fire on a cold start and stay running without needing to give it gas or restart and then it would run but stumble due to lack of enrichment and increase idle. Once warmed up enough everything would smooth out. Same somewhat for warm restarts, except you would have to keep cranking to get it to restart and then once it did it has to burn all the extra fuel dumped in before it stabalizes.

So you can start with that temp sensor if you want then move onto all the other stuff to save time.

Good write up. It sure will benefit a lot of members.
Thanks for taking the time.

Moneypit SEL · #12 04-06-2006, 08:25 AM

Quote:

Originally Posted by joel

This is actually what my indy told me, unburnt fuel, which is what he suspects to be leaky injectors. In fact, the CE light comes on and off when I step on the gas generously.

It should be easy to prove, then. If it's getting too much fuel, adding a vacuum leak will make an improvement in the way it runs. Too little fuel, and that vacuum leak will make it worse.