1986 Mercury Black Max XR4 Won't fire

[conner172]

I have a 1986 Mercury Black Max XR4 6 cylinder that just quit firing. I took it out a couple of months ago and it was fine, but took it out last week and it wouldn't even fire. I got it to start by jumping the battery with my trolling motor battery (24 volt) and it took right off. I almost didn't make it off the lake later that day because again, it wouldn't fire. I jumped it again and it took off. The next day, it wouldn't fire, and even jumping it wouldn't help, so I sprayed starting fluid in the intake and it started. I let it run for 30 seconds and shut it off, thinking it was okay. When I tried to start it again, it would not fire. Since then, absolutely nothing will cause it to fire - no jumping, no starting fluid, nothing. It turns over perfectly fine but will not fire. Please help.

 

[Laddies]

Re: 1986 Mercury Black Max XR4 Won't fire

STOP USING STARTING FLUID, it will destroy your engine. Your describition of the proble is not to good. If you have no fire, starter fluid won,t make it run that is lack of fuel. Jump starting has nothing to do with the Ign. system it gets it's energy from the stator, all the jumping will do is help the starter turn the engine. Go back and ck the engine for spark, if you have spark on all cyls. you have a fuel problem, if iut's a fuel problem I would prelube the cyls to help the starting fluid problem and ck compression then clean the fuel system, Get back and let us know what you find out about spark Bob

 

[j_martin]

Re: 1986 Mercury Black Max XR4 Won't fire

Conner 172
Please carefully describe the problem as you see it.
Does it crank slowly, or not at all?
If so, the battery's dead. It could be anything from bad connection to bad parts in the motor. Even if the motor is in great shape, it won't recharge the battery in a reasonable time. It probably only puts out a few amps to the battery, unlike a car at 100 amps or so. The battery needs to be checked out and charged.

Does it crank fast, but doesn't start. (fire)
It could be lack of fuel, or lack of spark. There are many causes for both. If you give this board detailed info on what's happening, someone will help.

Don't ever get anything but a gasoline and 2 cycle oil mixture any where near a 2 cycle engine as fuel. Starting fluid, carb spray, etc will take out cylinder and bearing parts in a fraction of a second. Back firing because of low octane could take out reeds and other parts. I've seen a lot of people use carb spray on snowmobiles. I've also seen a lot of blown snowmobiles. Could that be related?

hope it helps
John

 

[conner172]

Re: 1986 Mercury Black Max XR4 Won't fire

posted in error

 

[conner172]

Re: 1986 Mercury Black Max XR4 Won't fire

Oh wow - I didn't know starting fluid was a problem. :% It worked to get it going once, but not since then. I did check spark - there was spark on the one cylinder I tried, but it seemed weak to me. The plugs are the center fire type (no gap to set - just a little post in the center of the plug). I figured all of the cylinders must have spark but I didn't check. I'll check the rest of them and check compression, then I'll get back to you.

 

[conner172]

Re: 1986 Mercury Black Max XR4 Won't fire

John,
It turns over fine - beautifully in fact. It just won't fire. I'm checking the spark and compression later this week (don't have access to it now). The plugs seem wet like they're getting fuel. Spark seems weak, but I have no option of checking the spark gap as these are gapless plugs (the new kind, which I hate because I'm suspicious of them, but I can't get the old kind). I was unaware starting fluid was a problem and won't use it anymore. The engine is oil-injected, so the mix shouldn't be an issue. Sometimes when I used to start it, it would idle fine, but when I tried to take off it would bog down. That's what happened the day it finally quit. It bogged down, I let it idle a little more, then firewalled it and it took off. It had been flooded, I think.