QuestionThe valves are right beside the piston cylinder, in the block. When I pulled the head, both valves where closed at TDC, so I believe the engine was on the compression stroke. You have given me an idea, however. When I checked the engine compression after the rebuild, the most I could get was a range of 45 - 50 pounds, which I attributed to new pistons, new rings. The problem may be there. Thanks for the tip on the WD40, I always wondered about the increased cylinder pressure with starting fluid. I'll try the 12 volt start. Thanks for the replys and the tips. Happy Thanksgiving.
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Thanks for the reply. As a matter of fact, I pulled the head when I took the cover off the timing chain to check the sprocket marks for alignment, and made sure the no. 1 piston was at TDC. I took an old distributor cap and modified it to remove all the material except the spark plug terminals, so I could see where the exact location of the rotor is when the cap is in place. TDC and the location of the rotor on the no. 1 spark plug terminal is exact. I'd appreciate reading idea #2. (PS - carb's been rebuilt twice, and I installed a new fuel pump - good stream of fuel at the carb inlet, and I can see - and smell- it in the bottom of the manifold)
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Dick:
I'm restoring a 1937 Plymouth, model P7, and have run into a problem with the engine.I can't get it to fire. I took the engine down, and had it rebored, new pistons, rings, crank ground, valve job, all the things you'd do to rebuild.
I installed a new timing chain, and have carefully aligned the reference marks on the cam and crank gears. I have set the timing at 4 deg. after TDC per spec. I can get a spark to jump across a gap of 1/4 inch, and can see the spark jump across the spark plug electrodes. There is fuel present in the cylinders, and I have tried shooting starting fluid directly into the cylinders, but I can't get any detonations. Is it possible to create a resistance in all six of the spark plugs that would degrade the spark to the extent that the cylinder wouldn't fire? I've about given up on this engine, and am seriously considering a swap to a Mopar V8/12 volts. Any comments/suggestions would be appreciated. I'm 68 years old, and have been around the block a few times with other engines, but this one's got me stumped
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My guess is that the distributor is 180 degrees out of time. Take the #1 spark plug out of the hole, and stuff a tiny piece of kleenex in there, just far enough that it will blow out of the hole when the piston comes up on the compression stroke. Then put a wrench on the bolt in the center of the crank pulley and turn the engine by hand, clockwise, until the kleenex blows out. You may have to go around twice, as this is a 4 stroke engine. When you see the kleenex move, stop and find the timing mark and pull the crank slowly up to TDC. Don't back it up, always go clockwise. Now, pop the distributor cap off and see where the rotor is pointing. If it is pointed at #1 plug wire, I'm wrong, but if it isn't, pull the distributor and reinstall it so that it is pointed at the #1 plug wire WITHOUT MOVING THE CRANKSHAFT! Now the engine will run, if I've guessed right.
If not, let me know and I'll come up with idea number 2.
Dick
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Just to make very sure, you are sure the piston was at TDC, AND that the piston was on the compression stroke - right? You are aware that it could also have been at TDC but on the exhaust stroke, right?
You cannot tell by looking, you have to either install a compression gauge or stick your thumb in the spark plug hole, or by some other method determine which of the two parts of the cycle it is at - that is what I was trying to get at with the Kleenex trick.
You had a 50-50 chance of coming out right, and a 50-50 chance of being 180 out, the way you did it. If I were you, I'd double check that, because there aren't many other possibilities. OK, I'll quit flogging that horse if you are sure you are right.
If you've satisfied yourself on that point, all I can suggest is that you do a compression test on the engine - an engine with good compression, fuel in the cylinders, and properly timed spark WILL RUN, even if only briefly, regardless of the condition of the carburetor. If the compression test shows 100 PSI or more in all 6 cylinders, I'd temporarly put in a 12 volt battery, and try to start it while spraying a small amount of WD-40 into the top of the carburetor (that's a lot easier on the bearings than starting fluid). If it will run that way, even briefly, you can investigate the carburetor further - I have no other ideas.
Please don't give up on the original engine - they were fine engines, with a unique sound - everybody has V8s these days - an original car is getting harder and harder to find!
Dick
AnswerOK, you're welcome - I wish I could have been more help. Your compression numbers are VERY low - I don't know if an engine will run with that low a compression reading - there has to be something wrong there, if your compression gauge is right. The compression pressure for your engine should be around 120 PSI if you live at sea level, slightly lower if you live at high altitude, but even if things are not exactly right, you need about 100 PSI for it to run well.
The valves are both closed at the TDC on the exhaust stroke also on some engines - I don't know for sure on your engine but the older low performance cam designs were that way, - so you still have 50-50 chance of having the distributor in 180 out of time, but if you did, I'd expect some backfiring and popping back through the carburetor when you try to start it. If you don't get even that, I think you need to investigate why the compression is so low. Test your gauge (put it on your air compressor and see if the numbers agree), and if it's OK, I'd be suspicious of the valve timing first, if all 6 cylinders are that low. I know you were careful about it, but it sure acts like it's off a tooth or so, assuming the rings and valves are OK.
I'm going to be off for a week or so - traveling to visit family for Thanksgiving -so let me know what you find out in two weeks or so.
Take the week off and cook up a big turkey!
Dick
