Re: [diesel_mercedes] 240d engine in Jeep acting up

 

I'm lost after the injector swap


Following 

There's enough smart people here 

You'll have it solved soon

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------ Original message------

From: Bogy Wan Kenobi polespearbogy@ya...

Date: Mon, Jun 27, 2016 7:55 PM

To: diesel_mercedes@yahoogroups.com;

Subject:Re: [diesel_mercedes] 240d engine in Jeep acting up

 

I swapped the injectors (1 and 4) and the problem stayed with #4.

I also tested checked the clearances hot and they were intake 0.005" intake an 0.014 exhaust. I left them alone.

I couldn't do a hot compression test because my comp tester has a leak at the quick disconnect that has to be fixed. I will repair it  in such a way that I can use it to blow air into the cylinder to see where it goes - exhaust, intake, water jacket, crank case.

I began to wonder if there might be a piece of foreign matter above the valve (where the stem goes into the casting) that is holding it open when it gets hot. If warranted, or maybe if not, I will pull the manifolds before I pull the head to check for such abominations.

Getting closer,
Bogy,
 
"Hardware eventually fails. Software eventually works"                 - Michael Hartung


From: "Bogy Wan Kenobi polespearbogy@yahoo.com [diesel_mercedes]" >
To: "diesel_mercedes@yahoogroups.com" >
Sent: Sunday, June 26, 2016 10:43 PM
Subject: Re: [diesel_mercedes] 240d engine in Jeep acting up



I hadn't considered a sticky valve. But it would not be that bad all things considered. And it may be fixable with some MMO if it is just some sludge. Much better than a cracked head or piston to be sure. I like this engine and if the head comes off then so do all the rings. Plus cylinder dressing and a complete head job and timing chain.

What do you think about advancing the timing a bit, just 'cause, for that better performance you talked about? I have lower diff's (3.54:1) than the 240Ds came with, but the oversized tires more than compensate and I am in 15% overdrive now. A little extra power would certainly help, but not at the expense of the rest of the drive train. Actually 4.10 or 4.11 diff's would give me a very accurate odometer/speedometer and the engine would see the same load as if it were in the original 240D. But until then a little extra power would be desirable sans adverse side effects.

Bogy.
 
"Hardware eventually fails. Software eventually works"                 - Michael Hartung


From: "'Mark in Lakewood, CO' beeser750@q.com [diesel_mercedes]" >
To: diesel mercedes >
Sent: Sunday, June 26, 2016 9:04 PM
Subject: Re: [diesel_mercedes] 240d engine in Jeep acting up



The valves on these engines (and all other MB Single OHC engines) get LOOSER as the engine gets hotter.  So, if they're set correctly when cold, then they are most surly completely closed when hot.  Unless, they get sticky when they get hot....

Maybe a broken valve spring?  Other out-there ideas:  A bizarre crack in the piston that opens up when it warms up.  (Should cause more blow-by.)  Bent valve.  Some tiny bit of debris/dirt in the IP, injection line or injector.

The IP being 5 degrees retarded shouldn't make that big of difference, and besides, that would affect all cylinders the same.

By-the-way, you can advance the cam about 10-degrees by moving the sprocket one tooth to the right relative to the timing chain.  That would have your cam advanced 5-degrees, if it's now 5-degrees retarded, which would give a noticeable improvement in performance.  If the IP timing can't be corrected by rotating the IP on the block (it's mounted with slotted holes), it will need to be removed and reset onto the splines on the auxiliary shaft.

Mark in Centennial, CO

From: "Bogy Wan Kenobi polespearbogy@yahoo.com [diesel_mercedes]" >
To: "diesel mercedes" >
Sent: Sunday, June 26, 2016 2:15:40 PM
Subject: Re: [diesel_mercedes] 240d engine in Jeep acting up

 
Once it is warmed up the miss happens at all speeds.

I forgot to say that I had the pump off and discovered that the check valves in the lift pump were not sealing. So I corrected that.

I also determined that the #1 outlet is exporting only about 70% of the fuel that the others are. Yet when I crack the #1 injector line the engine almost stalls. Not so with #4. Cracking #4 makes almost no difference once it starts to miss. I will deal with that once the #4 problem is solved.

Also, there was a lot of air problems that I only discovered when I replaced all the hoses with clear lines. That made a LOT of difference. But I highly recommend clear flexible hoses if you possibly can.

Also there is a check valve on the IP fuel return outlet that I did not know about previously. That was stuck and freeing that up also made a lot of difference in the ability to bleed out the air and get it to start. 

As for the chain stretch, the crank was about 5 degrees ahead of the cam so the cam, and hence the IP, was retarded. Is that a significant problem? Even if so I can't see that being responsible for a miss when things warm up.

I plan to warm it up and pull the valve cover and check the valve clearances when they are hot to see if they are closing and thus affecting compression. But I am going into uncharted territory after that.

The only thing else that I can think of, and I just thought of it, would be a cracked head that opens up when hot. And THAT is not a happy thought. But I do not notice any pressure build up in the cooling system, nor a loss of coolant. But I will look closer tomorrow when I resume the investigation.

Thanks for replying,
Bogy.

"Hardware eventually fails. Software eventually works"                 - Michael Hartung


From: "'Mark in Lakewood, CO' beeser750@q.com [diesel_mercedes]" >
To: diesel mercedes >
Sent: Sunday, June 26, 2016 8:47 AM
Subject: Re: [diesel_mercedes] 240d engine in Jeep acting up



Is the miss when warmed up present only at idle, or at all engine speeds?

It's very doubtful that the compression will change in one cylinder more than the others after being warmed up.  Perhaps the efficiency of the injector could change with temperature, but this is also unlikely.

If the miss is exhibited at or near idle speeds, then this is usually due to air in the fuel line, or/and a weak lift pump.  From my experience, this will initially show up once the engine is warmed up, moreso than when cold.

If your crank is five degrees retarted relative to the cam (assuming the marks on the dampner/pulley are accurate), then your cam is 5-degrees advanced.  This would indicate little or no chain stretch, and would help performance, fuel mileage, etc.  

Mark in Centennial, CO

From: "Bogy Wan Kenobi polespearbogy@yahoo.com [diesel_mercedes]" >
To: "yahoogroups" >
Sent: Sunday, June 26, 2016 8:29:17 AM
Subject: [diesel_mercedes] 240d engine in Jeep acting up

 
Guys and gal:

I have successfully installed a 240D and manual transmission in my Jeep CJ7. After some grief caused by a bad injector in the #4 hole the idle stabilized to the point that you could "balance a nickel on its edge". The aforementioned grief was due in part to replacing the injector with another that was also malfunctioning. A third injector from the old 5 banger suddenly stabilized the idle and I have since pressure tested and spray-pattern tested all of my spare injectors. (At least all of them that I could find.) I had 6 bad injectors out of some 20 spares. I now have a complete set of known good replacements for both my jeep and my daily driver, a 300td. But I digress.

Although the idle is now stable cold, when the engine warms up it has a pronounced miss. Cracking the lines reveals it is the #4 cylinder again. I adjusted the valves with the engine cold (not sure if that was the right temperature) and ran a compression test. All 4 holes are within 8% of each other cold - hence the decent idle when cold.

My question is - what might be the reason for it to start missing when it warms up. And since it is a diesel the obvious cause is a drop in compression to the point that it cannot get the intake air hot enough to ignite the fuel. Basic physics. There is no evidence of a head gasket leak that I can detect and that leaves rings and valves, and/or possibly an injector that malfunctions when it gets hot. And a change of injectors with one from another cylinder would prove/disprove the injector possibility.

Oh yeah - I measured my chain stretch and when the cam marks line up, the crankshaft indicator is about 5 degrees after tdc. I know this will affect the timing to some degree or another and since the IP is closer to the crank it should be somewhat less than 5 degrees. Your thoughts here are appreciated. I have not compensated for this at the IP, yet. Could this be part of the failure?

I am willing to accept that the rings fail when they warm up. I have never seen that and I certainly don't like the thought of doing a ring job even though I will if it is necessary. I am more inclined to believe it is valves expanding when hot beyond the clearance limits. But when the engine cools down it again idles fine.

Any and all comments and flames and . . . are welcome.

Color me perplexed.
Bogy.
 
"Hardware eventually fails. Software eventually works"                 - Michael Hartung













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