'69 280SL auto ---running rich after sitting 6 mo.

[jonp821]

 Greetings ---  I have a '69 280 SL with Automatic trans and I let it sit to long, about 6 months, and it's giving me fits fouling plugs and running rough.

Car starts fine, idles at 1000 rpm and as it warms up to 180* F  it slowly drops down to 750 rpm.   

So far I have done a split linkage test.  When I move the FIP linkage up and down, nothing changes.  When I move the Throttle linkage portion forward and back,  the engine races. Seems like it is getting a full compliment of fuel with the pump disconnected.

I have done the linkage tour, just to refresh my mind, all adjustments were fine when I parked it and appear fine now ---no loose ball joints, Throttle plate closed at idle

At first it was spitting gas out the exhaust but I have taken the CSV apart, which was leaking, and fixed that. Replaced the fouled plugs, it ran fine for a few miles then started fouling plugs again.

I have measured the BC --it's at 21mm from nut to tip.  I have tried various shims ---makes no difference. I'm at approx 1000 ft altitude.

I have taken the WRD apart, the bulb is working to specs when put in hot water and the air slide valve is operating as it should.

I've tried lean adjusting the idle wheel on the back of the FIP, but it goes all the way CCW to where it wants to spin and it's still rich. if I turn it CW the exhaust turns black.

I've tried adjusting the idle screw on the manifold--- as I close it down the engine slows ---as I open it up the engine speed increases slightly ---but I can completely remove it from the manifold and nothing exceptional happens if I do other than a major whistling noise.

I've put a 5mm screw in the rack and it is not stuck.  It moves forward about 3/8 to 1/2 inch smoothly and springs back.  If I move the rack forward while the engine is running, the engine stalls.

I've checked the dwell, point gap and timing and all are in spec .

When I take it out on the road it accelerates as I would expect, very quick at full throttle and once the rpms are up over 2000 it stops missing.  The Trans seems to shift appropriately. The engine pops alot on deceleration.

I expected something to be stuck in the fuel system from it sitting,  but I'm running out of things to check---- any ideas what I may have missed??

Many Thanks in advance ----jon p

[rwmastel]

Jonp,
You've done very good diagnostic work so far!  You're clearly comfortable working on these cars and following sensible troubleshooting procedures.

I've never had a FIP apart, but aren't there check valves that can get stuck open?  I guess this would lead to rich running and fouled plugs on specific cylinders.  Do you have that, or are there signs of rich running condition on all plugs?

[jonp821]

Hi Rodd ----Thanks for the kind words.  I started taking go-kart engines apart when I was 10 so the wrench turning is the easy part.  Figuring out where to take it apart is another matter.   HA!!!

 The spark plugs seem to be uniformly carbonized but not wet.   I have tested the plugs when running with a strobe light and some seem to foul sooner than others.

I have not delved much into the inner workings of the FIP and have hesitated to do so.  Looks like this may be my baptism of fire.

I have been racking my brain and digesting all the info here in the tech manual of where fuel originates from and where it might be leaking.  I'm going to pull the injectors and test them, if for no other reason than to take them off the list.

I will look at where there might be associated check valves and see what I can find. 

Thanks for the tip---- jon p

[rwmastel]

Injectors could be more or less uniformly "bad".  That is a good thing to test at this point.

Do you have an ultrasonic cleaner?
https://www.sl113.org/forums/index.php?topic=37245
https://www.sl113.org/forums/index.php?topic=21188

Do you have an injector tester?
https://www.sl113.org/forums/index.php?topic=22683
https://www.sl113.org/forums/index.php?topic=30171

[jonp821]

Thanks for the links ---very informative. 

I have a hand operated injector pressure cleaner/tester that I got second hand and have refurbished it.  New seals, cup and gauge.  I've cleaned/tested some old injectors I got off ebay and some worked well, some not so good. I used techron injector cleaner on the funky ones ---seemed to clean out a couple of them.

Anyway----I'll give that a try and see where it leads--

Thanks again Robb---- jon p

[Bonnyboy]

6 months is not a long time to sit for a pagoda,   but I'm wondering how the fuel is.  I was chasing similar symptoms in my boat motor and finally drained the fuel - put new high octane ethanol free fuel in and some injector cleaner and the motor ran like a champ.  From one season to the next the fuel turned. 

I put in a new fuel filter in my boat every spring now and fresh gas.    I give the left over gas to a neighbour's kid who runs it in his old truck so I start fresh every season.   

[jonp821]

Hi Ian --- why is it you always overlook the simplest things.   I hadn't thought of bad gas.  The car had about 2-3 galls in it when I last drove it in February and that tank might have been a few months old then----over a year old now.  I did put 1/2 tank in it a week or so ago when I first fired it up.   Could be the gas got funky.

I'll change the filter and put some new premium gas in it to check that off the list----

Thanks for the input ----jon p

[Jonny B]

Jon,

Remember there are three filters in the fuel line: one at the tank (there is a nut at the bottom of the tank where this is installed), one at the inlet to the pump, and one in the engine bay, near the FIP

[bracurrie]

I have always heard that these mechanical injection pumps fail rich.
I believe the check valves at the top of the pump on each of the six supply lines to the injectors would if they were stuck open only affect what happens after the engine is shut down.
Ethanol gas sitting for a while can cause problems.

[Pawel66]

If I may, I would throw in my 2 cents. I am not an expert, but I went through similar struggles, so may have some practical observations. Every time I had issues (missing, hesitating, plugs with gas on them, getting a bit better on higher rpms, well she is still missing, you just do not feel it) after longer (few months) sleeping time - it was always the same: one of the plug connectors. I had Beru connectors, then one by one in the circumstances as above I replaced then with Bosch ones and the issues went away.

From your description you may indeed have your car tuned too rich anyway, but that is another story, perhaps, not causing the severe symptoms you describe, I am not sure.

But before getting to the FIP complicated issues and injectors, I would perhaps suggest:
- wait till it is dark in the garage, start the car, start the engine and check if you see any blue lightnings around plugs
- you can also get a thick glove, insulated pliers and, while engine is idling, remove connectors from plug one by one - where you hear the change of tone of engine - that cylinder is working, when pulling connector does not make the change - this cylinder is not working; I would start from cylinders that ha wet plugs when you checked them

If you decide to go the fuel way, if I may suggest, before you fill the tank with fresh gas, I would do the simplest tests:
- the fuel flow test, checking the rate at the end of the return line
- if bad, I would change the filters and do the checks after each one, starting from the easiest: main filter, fuel pump screen, tank filter (this may be tough to undo and also - you have to have your tank empty)

These are the practicalities I thought I would share

[ctaylor738]

See if the fuel return line is plugged.

CT

[jonp821]

 Hope every body who celebrated Thanksgiving had a good one.     I got quite a bit done on the car in spite of my relatives.

I replaced the fuel filter --- it had not been done in many years and it was pretty dirty and stunk like bad gas. There was gummy looking tan residue in the bottom of the canister.

Since the CSV was originally leaking like a sieve and all that gas was going somewhere, I changed the oil and filter for good measure.
   
I checked fuel flow in return line at the tank --- fuel flows like it was shot out of a fire hose--so the return line is not clogged.

I removed the injectors, filled my pressure tester /cleaner with Techron injector cleaner and they all open and close per spec.  They hold pressure without dribbling,  spray pattern looks good. I did get some black residue out of them.  They should work better.

I drained the tank ---there was only about 6 gallons in it.  It didn't smell particularly like bad gas as I had put some gas into it recently, the tank screen and pump screen looked clean.

Tomorrow I will put some fresh gas in it and see if all this has resolved the smoking and missing. 

I may even run it in the dark garage to see if the plug wires are arcing around the engine compartment as long as I'm at it.

I appreciate all the input and insight by those of you who have been responding to my foibles.---- jon p

 

[rwmastel]

Don't forget the fuel screen at the electric pump input.  May have some of that tan gunk on it.

[ja17]

Check to make sure your CSV on the intake is not leaking internally. You can temporarily dis-connect and block the fuel line to see if the problem goes away. Also take a fuel pressure check.

[jonp821]

Greetings All---

Sorry it took so long to up date -----

I decided to order some new NGK non resistor plugs since I had pretty much cleaned adjusted and replaced everything else during this test of my patience.  And since the old ones had kept fouling, I thought why take a chance on them.

The plugs arrived today,  I fired her up and the last round of cleaning, adjusting and replacing did the trick. She purrs like a kitten again!!

I am resolved to never let her sit in the garage without driving for this long ever again!!!

Many thanks to all the other members out there who put in their time and energy with me on this trial by fire----

Best regards---jon p 

[ja17]

Yes, it's amazing what a fresh set of plugs can do.  Cleaning the old ones, just does not do the trick most of the time.

[jonp821]

Hi Joe--- Yes the plugs were so fouled they wouldn't clean up and the bad gas really fouled the whole fuel system. 

It was one heck of a learning experience !!!

Thanks again All!!!----jon p