Weak spark

[gldavison]

Re: Weak spark

Thanks Gary,

I will be checking the compression tomorrow. I sure hope it is not valves hanging up.
Thanks for the reasoning and good explanation of the problem that you have seen past.
I am very thankful for this forum and the members that are so helpful.
Your right about the fuel being there, this is a for sure. I am still wondering about the spark, seems lame.
I checked at Napa for a compression gauge and they were about $60.00- I think I will find one to borrow for as often as I need one.

Thanks again for the helpful advice, sure appreciate all that has come my way!

Have a good weekend all
Greg

 

[gldavison]

Re: Weak spark

My saga continues...I have spark and fuel but still no go. I pulled one of the valve covers and removed the rocker arms on each valve and then manually checked each valve for travel and return. Each one descended and then sprung back to position. I turned engine over and with the starter and watched as each valve seemed to operate. I have not found a compression gauge so this was my test for a stuck valve. I am not going to check the other side till I hear back from you all as to if this is smart or not. So far 8 valves out of 16 are operational in my mind???

I spose if valves are all good then next is rings??? I hate to think of this, I have not even had it in the drink yet. I am beginning to doubt the owner whom I bought it from as he told me it was running fine when it was parked.

I am thinking that my next move is to check for compression with a gauge to either pinpoint the bad holes or celebrate with good compression in each. Where can I find the cylinder compression spec for my 1976 Merc 888 Ford, please?

Any and all suggestions are welcome, I am begining to get frustrated!

Thanks,
Greg

 

[gldavison]

Re: Weak spark

Hey I need your continued help- I picked up a compression gauge from autozone (borrowed) and am checking right now. After reading a dueling battle on how to check for compression I am going to notify my local fire dept and advise them that I am testing with all plugs removed.

Wow that was really a silly little squabble going on in that thread. Why the egos?

Thanks,
Greg

 

[wire2]

Re: Weak spark

I just realized, there's been no mention of ignition timing.

Loosen the clamp on the distributor and twist it a ways in either direction while cranking. I think you'll get some action.

Then put a timing light on it.

 

[Haut Medoc]

Re: Weak spark

Compression should be 150 (very good).....
To as low as 100.....​

 

[Haut Medoc]

Re: Weak spark

I just realized, there's been no mention of ignition timing.

Loosen the clamp on the distributor and twist it a ways in either direction while cranking. I think you'll get some action.

Then put a timing light on it.

I agree with this.....
Torque those rockers back to 20# & leave them alone!
The fact you have spark at the coil is irrelevant....
You do have spark at the plugs, correct?.....
Was the distributer removed at any point?
If you have spark at the plugs & push the throttle wide open & pour some gas right into the throttle plates, something should happen, even with poor compression......
One other thing, you should be able to disconnect the shift interrupt switch by simply pulling out the brown & black wires that are connected with bullet connectors in the back of the circuit breaker....
You have verified the firing order 1-3-7-2-6-5-4-8, in a ccw rotation on the cap with the rotor pointing at approximately 6-7 o' clock (#1) with the timing mark at TDC?....
& the starboard side from the front is 1-2-3-4 & the port side is 5-6-7-8?...

 

[gldavison]

Re: Weak spark

Ok, I just got done checking the compression and here is what I found out:

cylinder # lbs/cu i
1 112
2 76
3 75
4 80
5 109
6 110
7 112
8 130

I found this very interesting, what is going on on the left side? Could this be a head gasket? This variance seemed to far out of line. What does this tell you pro's? I'm waiting with anticipation for my next mission. Another weekend and I'm still in the dry dock.

Thanks for your continued help.

Greg

 

[wire2]

Re: Weak spark

The seal between 2-3 is gone, possibly the head is warped up a bit from a past overheat taking pressure off it.

Did you put the plugs back in and try twisting the distributor?

Go back a few posts if you missed the latest suggestions/info.

 

[gldavison]

Re: Weak spark

Wire2,
I did not attempt losening the distributor and rotating it yet but will next.

For the other recent reply; I have spark at the plugs now and I have tried spilling some fuel in the carb while cranking and nothing, not even a hint of a firing.
No the distributor has not been removed, at least not by me since I have owned this beauty.

I am not very confident in my experience of setting/checking the timing. I have only done this on single cylinder small engines. I am more than willing to try if I get some good instruction. You know that feeling of never having done something and not totally understanding it to begin with?? Yep that is what I have, but I am game to learn.

Thanks again all,
Greg
Go Pack!

 

[wire2]

Re: Weak spark

Just note the position now, you can put put it back after a try at some serious advance and/or retard.

 

[Haut Medoc]

Re: Weak spark

It should still run, even with the crappy #'s.....
Did you verify that the rotor is pointing at #1 when at top dead center by pulling out the plug, revolving the engine until compression is felt in that hole & then bringing the mark to TDC?.....​

 

[Boatist]

Re: Weak spark

Your making it way too hard. Start with the basics. For the engine to start need, compression 90 psi or more, Proper fuel mixture, Properly timed spark.
Find out what missing and you will find your problem in hours not weeks.

1 Compression in the cylinders 100 or more pounds. Easy to check with a compression guage. Do not pull valve covers or throw parts at it until you find the source of the problem.

2 Proper amount of fuel in each cylinder. After trying to crank for 30 seconds Pull a plug. Does it have fuel on it? Does it smell like gas? If you light a match does it burn? Is there water in the cylinder? This is the hardest part to check in my opinion and I think likely your problem. While you have the plug out does it have a gap about .035 inches?

3 Do you have a properly timed spark? From the posts sounds like you have spark. Do not start turning the distributer, instead put a timing light on number one and check it. No spark then put a dwell meter on and make sure Points set correctly. Last can make sure the cap has wires in the correct fireing ouder.

Try this
Do the compression test and check the timing first.
Then smell around the engine for fuel in the bilge. No fumes then pull the flame arester. Is the Choke closed? Poor in a 1/8 cup of fuel. Push the throttle to full throttle but be prepared to pull back if it starts to not over rev the engine. Crank the engine for 30 seconds. If it does not start do same again.

If it still does not start pull a plug and see if it smells like gas and will burn. Always be carefull with fire and make sure have no fumes in the bilge.

Choke could be stuck closed and flooding the engine but will uaually try and start. Carburator float could be stuck allowing way too much fuel into the cylinders. This should be pretty easy to tell by the smell when you pull the plugs.

 

[Surfdancer]

Re: Weak spark

Take a good look at the points cam in the distributor. Mine is worn and setting the dwell won't work by points gap alone.

Even if you get it to run, fuel economy will suffer if the ignition is not up to snuff.

On another note (related to this thread...)

Anybody know if you can still get electronic conversion kits for old Ford Prestolite distributors (Pertronix, etc)??? I cannot find any - they're listed but not made anymore. I don't want to drop $300 on a Mallory if I don't have to.

I put a Mallory breakerless distributor and a high energy coil and 8.8mm wires in my old John Allmand (1974 with the Mercruiser 888) and picked up almost 1 mpg (went from under 2 to almost 3 with a heavy boat). But it cost me about $450 by the time it was all installed

 

[Don S]

Re: Weak spark

That post is 6 months old, he did get it running. Of course, he then had starter problems.