I am working on a Rover raider with a tecumseh Ov358ea 13.5 engine.
It has had issues starting since I've had it, in fact I've never got it running. It will turn over but fail to fire and then cough out of the intake.
I though it may have had a stuck valve but have check the valves and adjusted the clearances (they were within tolerance anyway) but still no good.
I now think it may be a head gasket or the fly wheel key has sheared so my first question is:
What does correct ignition timing look like regarding the coil and the magnet? I understand that a few degrees advanced timing is ideal but does the following picture suggest too much advancement??
For context the engine is currently at TDC and both the intake and exhaust valves are closed.
Yep tried starter fluid to no avail. I pulled the head off and broke the head gasket in the process, not supprisingly.
There was significant carbon build up which I cleaned and polished and then put it all back together. It coughed and idled for about 2 seconds before stalling again.
Hopefully the local has a gasket kit for these tecumsehs
You may be lucky to find a gasket, they have been out of production for many years now though. Does it have good consistent spark? Not impossible that it is the coil itself. A quick google says 10-35 degrees btcd so that looks ok.
Personally i would have started with a compression test, than a leak down test to rule out mechanical. one other check is valve timing, easiest test for that is at TDC (not comp stroke) the both valves should rock.
Good spark from the plug but I will try a new one just in case. I should be able to compression test it when I get my kit back tomorrow (leant it out).
It does surprise me a little that non OEM tecumseh parts don't seem to feature in Google searches for spares....
Out of curiosity what did you set the valves to? a bit of research online is telling me that valve clearance is critical on these. I do vaguely remember having a similar problem with one but was many years ago. According to the manual it should be a very tight .004" on both intake and exhaust
Tecumseh shut down production in 2009, and yeah unlike briggs and honda aftermarket has so far not really gone anywhere. We struggled to get genuine parts 10 years ago.
I am not a big fan of the tecumseh engines at the best of times
OK, it's not the spark plug. Strong blue spark clearly visible.
So it getting spark, It's got plenty of compression and it's getting fuel directly (ill worry about the carb after ive got it to urn over/idle momentarily)
I went back to the flywheel key thinking that it may have sheared to the point that it was 180 degrees from where it should be and I just didn't realise when I first inspected it.
Unfortunately it is not the case. After removing the flywheel the key is still in perfect condition.
The stator is very dirty however and wondering if a dirty stator can reduce its performance?? 🤔🤔🤔
I've taken the exhaust off and tried it on the off chance it was clogged - same result.
Leak tested the head with coloured water and determined there is no blowby occurring at the valves as the fluid remained constant for 15 mins and towel underneathshowed no coloured water.
No scoring or abrasions on the cylinder and the head gasket is still in ood condition.
Something obvious we are missing here. Have you checked the cam timing, making sure the valves are opening and closing in the right sequence relative to TDC?
Don't worry about pulling it apart to check the cam timing, just get it up on compression stroke then rotate the motor through its cycle to make sure the exhaust valve starts to open after it has gone over TDC and follow it through the cycle of the exhaust valve shuts and the inlet valve begins to open. Probably best to check with the head in place, doesn't matter about the gasket at this stage
Does a visual check of the valves (and an u derstanfing of where TDC is) not represent the camshaft timing??
In other words, with the valve cover off and spark plug out using the trusty screw driver method and spinning the flywheel to find TDC any discrepancy with the camshaft timing should also be evident....??
Or is there something else in the camshaft timing that can't be determined without gaining access to it?
Just don't want to rip the engine off the chassis and get in to the guts without understanding the requirement first.
Edit: Sorry Norm, just saw your response on the previous page
The valves and timing appear to be functioning as they should with both valves closed at TDC
The valves and timing appear to be functioning as they should with both valves closed at TDC
On TDC the mechanical compression release has one valve slightly open on TDC,
Never adjust Valve clearances on TDC when a Compression release is used.
I would usually disconnect the coil kill switch wire just so you know it's not intermittently earthing out.
I like to swap the coil just to rule that out as having a problem under load but if you don't have a spare you wouldn't want to spend thirty dollars for nothing if it's not the problem.
The service manual would explain the adjustment better , All I could find was the following, Valve clearance spec is .004" , and yes at top dead center of *compression stroke* , plus about 5 degrees of additional flywheel movement (piston moves down about 1/4" after top center) - Or, set each valve one at a time by turning engine until one valve opens fully, set clearance on the other valve, until both valves are set.
If you don't have the manual but know the clearance is .004 " then I would set each valve one at a time by turning the engine until one valve opens fully then set the clearance on the other valve.
So after setting the cam timing again and reinstalling everything it eventually kicked over and idled very roughly for about 10 seconds.
I also set the valve clearances in the way Max suggested (with one valve open and the other fully closed.
It surged a few times then died and I'm sure it was running off aero starter rather than fuel from the carb.
Is it normal for the starter motor to cut out and then re-engage the flywheel when trying to turn the ignition on? It seemed as though it was making the engine cough when it was doing this....
Is it normal for the starter motor to cut out and then re-engage the flywheel when trying to turn the ignition on? It seemed as though it was making the engine cough when it was doing this....
The starter pinion is on a lead screw so when the starter spins the pinion gear engages with the flywheel but when the motor runs the flywheel is spinning quicker than the starter so this will disengage the starter pinion.
If the motor fires or runs while cranking then it is normal for the starter to disengage .
