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Need help again on my 135 opti

tom_c

Member
"I go thru this every October.

"I go thru this every October. The 135 opti ran good for 5 days on a trip and the 6th day it shut down to 1500 rpm with radical rpms at idle. It also sounds like a bad knock in the engine. I cleaned the fuel tank again, changed the plugs, put new air injectors in and put a new TPS on it. The knock is gone but the engine cranks up and sounds like it has a couple of cylinders not firing. It also cranks up sometimes and goes right to wide open throttle other times it surges from 600 to 1100 rpms. Lots of raw fuel coming out the exhaust too. Checked all the connections. Any suggestions? (2000 model)"
 
"Suggestions, yes, get rid of

"Suggestions, yes, get rid of it. The 2002 and earlier Opti's had numerous bugs.

Still sounds like a bad sensor, ECU or a ground fault somewhere.

Best chance of finding the culprit is paying the cost of an hours service at Merc and having them plug it into a DDT to get a read out of what has gone bad..."
 
"Thats my thoughts to Graham.

"Thats my thoughts to Graham. I had it on the laptop and it shows no faults or errors. I have been running it everyday on the hose trying to get it to blow up or just put hours on it until the laptop shows an error. The shop I use for parts and labor feels so bad about not being able to find the problem so they have been hooking the laptop or DDT on it for free. I know how hard it is to find a ground fault. What do I look for when the laptop does not show any system faults?
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"
 
That's where you start wit

That's where you start with a timing light. See if it's losing spark to a particular cylinder or a couple cylinders.

It could be a poorly grounded coil or even a dirty pin in the harness - which is maybe where you could start.

Unplug each coil from the harness (one at a time) and use some circuit board cleaner (available at any electronics place) on both the pins at the coil end and the harness connectors. Then put them back together with a bit of dielectric grease. I would even go as far as to remove the coil from it's mount and clean that up as well with a bit of steel wool or sandpaper - just to make sure it's grounded well to the block.

At worst you will have solid ignition connections.

If the CPS (which is the trigger on these hi-tech gadgets) or a individual coil was bad you would get an error code - so I would shoot for the ground fault first...
 
"Ok, thanks Graham. I will try

"Ok, thanks Graham. I will try that in the morning and report back. I like the "yes, get rid of it " answer the best.
"
 
Update : I took every connecti

Update : I took every connection loose and cleaned every elecrical part. Put it all back with grease and fired up the engine and all was well for about 3 minutes. I thought the problem was solved but it went right back to running rough and spitting lots of raw fuel out the exhaust. It acts like it is running with the choke on. I am wondering if there is a hole in the diaphram pump letting fuel into the crankcase. Is that possible?
 
"That is definitely a possibil

"That is definitely a possibility. Usually obvious, because if the diaphram is torn, the primer bulb will not get hard and you can hear the fuel spilling into the crankcase.

The one problem that the diagnostic software will not identify is when the ECU is malfunctioning."
 
"I put the engine back on the

"I put the engine back on the CDS again today. No faults on anything. Ran all the diagnostic tests and no faults. Ran the engine running test and let the computer drop each cylinder one at a time and when #1 dropped the engine quit. Dropped #2 thru #5 and the engine gained rpm's
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each time one was dropped. When #6 was dropped there was no change in the engine. #6 is the one I think runs the diaphram pump. There is no where for that much raw fuel to come from. I will take the diaphram pump off next. I will also hunt for a used ecm to borrow and see if there is any change. Thanks for all the help and keep any ideas posted."
 
I spent 230 dollars in parts a

I spent 230 dollars in parts and labor and a few hours on here asking for help. If you read the above posts you will see what a 15 dollar part can cause or should I say fix. The diaphram on the vacum fuel pump had a rip in it causing gas to get in the crankcase. Amazing how this affects an optimax. It really was not detectable until the hole was large enough for lots of gas to come thru. Until it was noticable in the exhaust it caused a multitude of symptoms. A very good lesson learned. Now its only 15 dollars to fix it. I wonder how long before the next trivial problem starts?
Thank you all for your help.
 
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