not running well?

[james1115]

hello I have a 1986 merc 90 6cyl. OK here it is, when I am at neutral my engine purrs like a kitten with the occasional jump in RPM's but once under a load it sounds awfull. It cuts in and out up untill about medium throttle then from medium throttle to full it boggs down and sounds like it is getting too much fuel or something. the whole time the rpm's are jumping up and down up and down. well I just replaced the power packs and cleaned the carbs hoping that would be it but no dice. well If anyone has had the same problem please let me know. <br />thanks<br />James

 

[Oldsaltydog]

Re: not running well?

Possible fuel problems to look into: old gas, water in the gas, clogged fuel filter, clogged fuel pick up line in tank, plugged fuel tank air intake, bad primer bulb, leaking or restricted fuel lines, weak fuel pump, malfunctioning choke, improper air idle mixture, and fouled plugs, etc.

 

[achris]

Re: not running well?

James,<br /><br />Sounds like a high speed stator. These engines effectively run 2 seperate ignition sytems. Each system has the following components: a 2 speed stator, a switch box, a set of triggers and the coils for each cylinder. The 2 speed stator is high and low speed. If you look at the switch boxes you'll see each has a blue wire and a red wire. One of these pair (red and blue) has a white stripe on it. First make sure that the both wires with the white stripe go to the same switch box (doesn't matter which one). The blue wire is the low speed and the red wire is the high speed. Change over occurs at about 1800 RPM. The jumping of the revs is due to the fact that as the engine speed increases and the output from the low speed stator (one of them) decreases, you loss 3 cylinders. What should happen is that the high speed stator takes over, but it's not. Because 3 cylinders are now 'off-line', the engine speed drops, back into the range that the low speed stator can supply enough power for pack to fire those cylinders again. They kick in and the engine speed increases to the point where the stator cuts out again and so it goes on...... (bit like me really) This can be a b**** of a fault to find because of the engine speed thing. Let us know how you get along....<br /><br />Chris........

 

[james1115]

Re: not running well?

hey ACHRIS60 you have no idea how happy that makes me to hear you say that. I have been battling this problem for a long time now trying to eliminate one thing at a time. I already have the new stator on order and I am gonna put it in tomarrow. I hope all goes well but thanks so much.<br />James

 

[achris]

Re: not running well?

James,<br /><br />Glad to be of service. Let us know the result.<br /><br />Chris........