5m no start (back fires through intake)

[buhay6]

ok as the title says I got a 5m in my 84 p -type and I just finished rebuilding the top end. Went through everything to make sure it was hooked up right and everything checked out, so I went to go start it and it wouldn't start. I re checked my timing 3 times and it was perfect, I'm getting spark at the coil pack and I'm getting fuel to the rail. I'm doubtful of it being the dizzy because I marked the old position of the bolt on the slide to hopefully avoid this problem. I noticed it was back firing through the intake system which makes me think again its timing but I've re-checked it 5 times already and its still good.

If some one could help me out with a good link or info that'd be awesome. I've searched the forums for a while now looking for someone who had the same problem and I came up empty.

[CarlH]

Go the the TRMS book and check the cam timing over again, Make sure the key in in the crank pulley properly and the cam pulleys have the proper settings,, then I would look at the lifters and rocker arms to be sure the valves are closing all the way.. do a compression check to see what your getting and try to listen to hear the leaking air in the manifold.. Carl H

[FranK]

You probably have a misalign of the Gear on the distributor.

Unscrew the plastic cam cover, rotate de crank to have the cylinder no1 at TDC on the Compression cycle.

Then pull out the distributor and align the gear with the mark on his housing then plug it IN.

Normaly the engine should start and run if you had the good timing on the mechanical part.


Now time the engine with a timing light, don't try to rely on the marks you had done to avoid timing with a timing light.

[buhay6]

thanx for the help guys I guess i'll tear it back down and try it again.
the compression before pulling the head was:
#1-170 psi
#2-168 psi
#3-170 psi
#4-140 psi
#5-170 psi
#6-150 psi

I had HG failure at cylinder 4 and 6, which was why I pulled the head in the first place.

I know this is a big time noob question but I've never used a timing light but how do I use it? does it just plug into the ingition coil?........screw it i'll just look it up

[bodyrollzero]

sounds obvious but make sure your cam gears are on the right way. when i rebuilt my motor i had the same problem and realized that the exhaust cam gear was on backwards giving me the wrong timing. im preddy sure the gears are the same right and left only one is used reverse facing of the other.

im also quite sure that if the engine is firing out of the intake ignition cant be the only problem

[buhay6]

Ya the more I think about it the more i realize I probably put the gears on the complete opposite way they came off. I just thought a time mark was a timing mark, my bad. I'm pretty sure the intake cam is on exhaust stroke and the exhaust is on the intake stroke...... if that makes sense.

and ya the cam gears are completely identical.

[tyrantfour]

the intake cam gear has the lip on the outside and the exhaust lip should be up against the rear cover. backfiring out of the intake tells me its getting compression, fuel and spark. but the power stroke pressure is escaping through the intake valve. you should be able to open the oil fill hole and see the timing hole on the camshaft itself. if in perfect time, the hole on the cam will match a hole machined into the cam tower. open the oil cap and youll see what i mean. if your 180 out then you WILL know.

[buhay6]

well I looked at that when I installed the cams into the cam tower, I had it bang on as specified in the haynes manual. I dont know it the oil cap holes going to be big enough, I'll just take the valve covers back off and double check that the holes are still lined up.

[fvaldez421]

Your timing could be accurate but did you tension it right? I pulled my head and replaced all my seals except the cams (which were done before) and found myself with the same problem. At first, I didn't tension it correctly and it jumped a tooth, but I later tensioned everything right and the car started and ran VERY rough. Then my neighbor, suggested I check or replace my points (dizzy rotor and cap) my wired looked pretty old so I said what the hay! And I had some rust between the rotor and spindle. And the actual rotor contact was loose. After I replaced all three, it returned to its originall beautiful humm. Check your timing belt for tension and your points. Even if your getting a spark at the end of each wire, maybe its not as strong as its supposed to be.

[Dakar2008]

i'll post a picture of how it should look. when proper