• Hey Guest!
    British Car Forum has been supporting enthusiasts for over 25 years by providing a great place to share our love for British cars. You can support our efforts by upgrading your membership for less than the dues of most car clubs. There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Upgraded members don't see this banner, nor will you see the Google ads that appear on the site.)
Tips
Tips

A little ignition help needed

Share this page

I am trying to steer the troubleshooting in a logical flow and prevent unneeded disassembly. The 0 compression is unusual. Thats why I want the other 3 cylinders checked to both prove the measurement process and to determine how many cylinders may have a problem, if any. Once we determine compression is correct we will move on to fuel and spark. If there are compression problems, they need to be corrected first. I hate to change parts unless they have been tested and found bad. All the suggestions are good ones, so far.
 
The carb is a Webber DGV. What I mean by air and fuel being pushed up and out the top of the carb when cranking with the ignition key is just that. It is not being sucked down into the intake manifold and into the cylinders then out the exhaust. One of the first things I had done was install new plugs, then new plug wires, rotor and distrib. cap. I took out the points and they looked good so I re-installed them and set the gap to .015". I will check the timing tomorrow as Startech47 suggested and see what I come up with. I am thinking that if the valves are closing when they should be opening, that may be what is causing the air and fuel being expelled out the top of the carb. instead of flowing properly through the engine. I will also verify the compression of the remaining 3 cylinders and use the scope to verify piston movement and valve function.

Thanks for the info (however, I sure hope you are wrong about the cracked block or head :smile:)!!
Bob C.
 
Actually, I don't think there's anything serious wrong. I just can't put my finger on it, and I know nothing of Webbers. I'm inclined to believe this is entirely a fuel problem but someone who knows about those Carbs will have to step in with something helpful. I'm assuming that compression reading is wrong, but someone who knows the equipment you used and symptoms impacting compression can likely help best. Sorry, if I knew more about Spits or Webbers I could do more for you. You'll get it fixed soon, I'm sure.
 
You can check to see if your timing chain has skipped a tooth with out pulling too much apart.
Mark the location of no. 1 plug wire on the base of the distributor and remove the cap. Remove the rocker cover. Rotate the crank so that the timing mark is at or near TDC and the inlet valve on no 4 cylinder is just opening and the exhaust valve is just closing. The last sentence is important. The position of no4 cylinder valves determine what stroke you are on. If they are not where they should be turn the crank 1 revolution and align the timing marks again.
Once you get this accomplished the rotor should point to the mark you made on the distributor base.
If you can't get this to allign then the problem lies under the timing chain cover.
I don't think your timing chain is broken since your rockers are moving. More likely the tensioner has broken and it has slipped a tooth or two.
If your cam timing is off then your valves will be open at the wrong time this would allow the engine to not build compression. And create the symtoms you are seeing.
 
I'm not sure if you've already answered this, but what equipment and method are you using to check compression, and have you tested your equipment on another car?

I agree that if your compression info is correct, and the crank turns without resistance, there's a real problem, and a good start would first be another examination of the valves under the valve cover, then under the timing cover.

I'd be sure your valves are opening and closing correctly and that nothing really does look broken, snapped or otherwise inoperable under the valve cover. If that checks out, I think what the others here are saying about the timing chain could have merit, but I'm having problems seeing how even a skipped tooth or link could do what you are describing.

I believe that zero compression in a cylinder would mean that the valves are never closed, assuming the rings are good and your head gasket isn't horribly blown. If those other issues don't exist, then the cam lobes, I would think, would prevent "zero commpression" from happening, regardless of whether the timing gear is off.
 
I am using a new compression tester screwed into the spark plug hole in the head. Throttle wide open and cranking the the engine for 5 to 10 seconds.

Does anyone know what would cause the air flow being pushed up and out the top of the carb while cranking the engine? I mentioned in past posts that it is "air AND fuel vapor". However, I think the "Fuel" part is just a result of the air flow.

I'll get back to checking everything again and get back to ya with the result later on today. Thanks again for everyone's help. I cretainly do appreciate it!!

Bob C.
 
rcufley said:
Does anyone know what would cause the air flow being pushed up and out the top of the carb while cranking the engine? I mentioned in past posts that it is "air AND fuel vapor". However, I think the "Fuel" part is just a result of the air flow.
Click to expand...
A really wild cam can do that, but more likely I think is a stuck (or broken) valve or cam timing that is way off.

The carburetor doesn't really "care" which way the air is flowing, it will mix fuel with it either way. But unless it's actually sucking air in through the exhaust, the air came in through the carb and picked up one load of fuel, then picked up another load as it came back out.
 
Just finished re-checking all four cylinders. I used a socket on the crank pulley nut to rotate the crank while viewing the internal operation with an inspection camera placed on the open spark plug hole. I could see the valves and piston moving in each cylinder while rotating the crank by hand. I then removed each spark plug,one at a time, to check the compression in each cylinder. I cranked the engine over with the throttle wide open using the ignition key for approximatly 5 to 10 seconds on each cylinder. Result: Zero compression on all 4 cylinders. The needle on the gage did not even move off the zero stop at all! The gage is new and does indeed register when I push air into it using my air compressor. I will either try Startech's or Rhodyspit's advise or maybe just go straight to removing the timing chain cover tomorrow or Wednesday. Hopfully I will find a busted tensioner.:smile:
Thanks again for everyones help.
Bob C.
 
It would still be worth while to check the timing before you take the timing cover off. As much for our curiosity as for your trouble shooting.

With those results it is looking more likely that you will need to remove the timing cover. Make note and let us know if the crankshaft nut is tight when you take it apart. It could be a sprocket, tensioner, chain, or key problem. If the crankshaft nut is loose it may be a key problem.

Also, take note of the orientation of the crankshaft oil slinger washer, in order that you reassemble it correctly. It is worth taking a picture. Check it's condition as well.

Thanks for the compression figures. Good news on the inspection camera results!!!
 
Somehow, as others have said, your timing chain and cam would have to be sufficiently off, somehow with the valves in all cylinders being open during each compression stroke. That would mean that despite each cam lobe being fixed, of course, the cam is now so far away from proper timing that not a single valve remains closed on the compression stroke.

I guess that is possible.

If your timing chain jumped so many links that the valves are never shut when they need to be, I suppose that might explain both the compression problem and the odd situation at the carbs. Maybe the intake valve is open at the top of the compression stroke.

If you are certain then that you've got a good "zero" read on all 4 cylinders, I'd pull that timing cover and see what's there.

Out comes the coolant, radiator, fan belt, damper pulley, engine support bar and a bunch of nuts and bolts and maybe the generator/alternator. You'll need a spare timing cover gasket and some good sealant.

If someone another idea, maybe some time and effort could be spared, but it's sounding like there is no other alternative. A misaligned timing gear could result in the chain jumping, and so could a weak tensioner, and I'd sure be careful how you put things back together if you find a problem under that cover. Sometimes there's a reason for a failure other than just age and wear, and it may not immediately be obvious.

I've seen weak tensioners, and even ones that slid off their pins due to a broken or missing washer. But in those cases there was no doubt what happened. The noise and rattling was quite loud, and in one case the tensioner had worn a hole in the cover.

Good luck and tell us what you find.

PS Even the woodruff key at the crankshaft sprocket should be examined. Hopefully, it's tight and in proper alignment.
 
Yes KVH, I am expecting a dramatic change in timing that would easily be seen by the timing test, not a few degree change. I am asking for the test since it was one of the less likely reasons. Why this has happened will have to wait for the tear down.
 
I agree it would have to be more then one tooth. I can't think of anything but cam timing that would give zero compression across the board. Well nothing that wouldn't have made a lot of noise when it happened. I think when he tries the test I suggested he won't be able to line things up. It might be time to change this post from "A little ignition help needed" to "Timing chain replacement".
 
Maybe a more appropriate post title would be "Oh NO!!! What the heck have I gotten myself into now? " :smile:) Been kind of busy today, will try to get the test done tomorrow and get back to you guys.

Bob C.
 
If he jumped enough teeth, he's bent all the valves. That's the only thing I've ever seen that killed the compression in all the cylinders. I saw a 318 Chrysler v8 cam timed on #1 instead of #5 and all the valves got bent when it was cranked over.
 
Depends on the design of the engine. If it was a Honda or E-type Jaguar the valves would be bent.

Glen's E-type was stolen and drag raced by the person who stole it. They destroyed the automatic transmission and bent all of the valves. They than proceeded to park it back in the same spot it was parked before it was stolen. The insurance would not pay for any of the repairs.

I do not believe the 1500 is a zero clearance engine and the valves may not be bent.

Run the test. If the timing is off repair the timing chain. Re-run the compression test and we will proceed from there.
 
Actually, if he did bend any valves, there will be excessive clearance between the rockers and push rods when the valves are closed. Easy to see.
 
:iagree: Remove the valve cover and that would be evident.

If they are not bent, I would bring the engine up to TDC on #1 and #4 cylinders using your little borescope. Then check the the position of the valves in cylinders #1 and #4. One of them should have both valves closed. If neither have both valves closed, then there is definitely a mess up in the valve timing. That would cause the zero compression.
 
Ok this is a bit of a stupid guestion, However, I have to ask it anyway... Which valves are the intake valves and which are exhaust? I can not seam to find it in my manual or on line. Thanks.
 
Ok, With all spark plugs removed and cranking the engine by the crank pulley nut I see all valves opening and closing using that little bore scope I have. Removed the valve cover and checked the valve lash at the rockers. All are set at .010". All rockers are rocking and I can not see anything busted or bent under the valve cover. I rotated the crank to about 5 degrees after TDC and the aft valve in cylinder #4 is wide open and both valves in Cylinder #1 are closed with the rotor pointing to where the #1 plug wire was located on the Distrib. cap. I also checked the position of the piston for cylinder 1 in relation to TDC on the pulley and it all lined up, piston at the top of the throw and the timing mark pointing to Zero TDC. I just don't get it?? I would assume with these results the timing would be ok. With what I have seen by trying to start this thing (and having all the air pressure coming out the top of the carb) I just can not imagine the problem NOT being a timing issue. Anybody out there think I should go ahead and pull off the timing chain cover?
 
Back
Top