Engine surging at high load/ high rpm

High all,

I have searched the forum and haven't really found an answer. I've got a 1986 SN with a 351W, electronic ignition, Holley 4 barrel.

Here are the symptons:

Running in the yard on hose:

Engine starts, idles smooth, runs good up to ~3200 RPM. If I add additional throttle, it surges between 3000-3400RPM. It will continue this indefinitely. If I try to rev higher it bogs and sputters worse. If I back off, it runs smooth.

Running in the lake:

Starts fine, runs smooth, takes off and gets on plane at 1/2 throttle or so. At full throttle it sputters and won't get on plane.

If I drive around for a while, the sputtering starts at lower and lower RPMs until finally it won't even run when you go from neutral to forward.

I have replaced water filter/separator, drained some gas from tank (had some water), still didn't run good. I have now replaced the fuel pump and it still surges when running in the yard. I don't see any point in dragging it back to the lake now since it won't get above 3500 RPM on the hose.

I rebuilt the carb last year, not sure if I did something that would cause this problem...


Any troubleshooting tips? I am convinced it is a fuel issue, since it runs perfectly smooth up to 3000 RPM. I am thinking an ignition issue would show up sooner.

Maybe it is sucking air and leaning out at high RPM??? I'll try spraying ether around the carb next and see if that smooths out the surges.

Thanks in advance for any help!
Keith

Pertronix. Have had the electronic ignition for 5+ years with no issues. Same distributor, just replaced the points with the electronic components.

EI's are known to have problems.   Your problem sounds heat related, as it gets worse when the engine has been running for a while.   Read up on the Pertronix failures, and then on coil failures, I think either is a possibility.   If you do end up with a new coil, don't get an oil filled one, they tend to breakdown quickly. you'll need to get an epoxy filled one for longevity.   BTW, searching the site through google seems to be a bit more reliable than the search feature :)   

Did you check your antisiphon valve?

First described as fuel starvation but after reviewing the video, its quick recovery and repedidness i want to say ignition. Usually fuel starvation will pop and fall flat and not recover like that.

1) Throw the breaker plate and points back on as a test. Pertronix do fail if different ways. I really suspect the igniter is failing. You do have the breaker plate in the glovebox, right?

2) if you still suspect fuel, you could find an outboard fuel tank, and run the boat off that as a test. Just plug the line to the tank well.

Clean the ei setup and check gap

Ok, getting close now. I put a timing light on the plug wires (one at a time) and noticed when the rpm dropped, there was no spark to 3 cylinders! I swapped a couple plugs and wires, even re-routed the wires to put the distributor on 180 degrees backwards. Still the same cylinders were not getting the juice!

I am thinking it is definitely the EI setup now...

Ok guys, after fiddling and letting the boat sit for 3 years, I'm trying again to figure this thing out. It is definitely an ignition problem, but I've changed the coil, pertronix ignition, wires, plugs, cap and rotor all to no avail...

Any ideas on how to narrow this down?

This is a little bit of a toughie, a couple variables going on with the alternator, and EI conversion kit etc. Could you do a chronilogical time line. I'll start what I mean, and you can fix it and add to it.

Summer 2002: Boat Running fine

Summer 2003: Added EI Conversion Kit

Summer 2004: Battery not charging

Summer 2004: Got new 1 wire alternator

Summer 2005: Engine started hesitating etc.

Summer 2006: Noticed boat dying after 1/2 hour etc.

Something like that, add as many potentially relevant details you can think of and put them in the correct order.

new86owner wrote: I'm thinking of taking the belt off the alternator and seeing if the ignition issues are still there. Does that sound like a good troubleshooting step?

I don't think that will hurt anything, but not sure it would help. I guess you would be no worse off than you are now, not charging. And, if the ignition issues went away, I guess that would be a clue.

1.) At this point, do you basically charge the battery with a plug in charger every time you want to use it, then go out for a 1/2 hour until the battery runs down, then die out?

2.) When you gave your voltage readings of 11-12 then 14 with the motor running, where were you getting the reading from, the dash?
A better trouble shooting step would be to put a voltage meter (multi meter set to 12 volt battery voltage) right on the + and - battery terminals, and see what you're getting with
*ignition off
*ignition turned on engine off
*engine on
*engine on and revving

My only theory as that something is grounding out in the area of the distributor, messing up your spark and drawing everything down. You mentioned above that 3 of the cylinders weren't getting spark, sometimes that can happen if you have too much play in the dizzy. I'll ask the question of others, could that cause the distributor to ground against the block also?

One quick question/check. When you converted to the one wire distributor, what did you do with the extra two wires? Are they tied up out of the way, not touching each other and not touching the block?

Your alternator should charge or its broken or not connected to the battery due to a bad breaker or bad wiring. Take off the alternator and have it tested and your friendly neighborhood auto parts store, if it is no good get another one.

How it is running Sounds like a classic low voltage to the ignition system from the ignition switch problem to me, don't know if you have a resistor or not but you should measure voltage that actually reaches the resistor from the ignition switch while you are running. Your alternator problem could be making this worse, new parts and a fresh battery could mask it for a little while.. but the root cause would still be an inadequate set of wiring.
.

It sounds like you're starting to get warm now.

Good work on connecting that alternator wire. Hopefully no damage was done to the alternator, but it sounds like you caught it in time. That should stabilize your voltage output and hopefully fix the charging issue.

Not sure if the voltage being all over the place would affect your ignition or not, but it's possible.

I don't know much about the electronic conversion kit you used, but I don't believe the collar is supposed to be a wear and tear item. It sounds like it just fell apart on you. But, at least you know part of your problem lies there as well.

I am having the same problem with my 87 supra sunsport with the 351w and the same Pertronix ignition (mine ignition is 9 years old). I have chased this problem from fuel pickup to fuel filter to fuel pump, carb rebuild, cap and rotor, new plugs , new ground ran from block to motor, cleaned/checked all electrical connections and still no answers. This thing runs and starts better than it ever did but then the surging happens and its a big punch to the gut and a huge hit on the ego. I really hope you have shed some new light on my problem. Hopefully you have found your problem and if so you may have saved my summer as well. Please keep us posted! Fingers crossed you got this figured out!

OK guys, finally figured it out. I installed new magnetic pickup, rotor button and advance springs. Started it up. Same issue, runs good up to ~3,000 RPM, then misses and fluctuates between 2-3,000 RPM. While I was installing the components, I noticed some vertical slop in the distributor shaft. Hmm... I think what has been happening is that when the RPM increases enough for the advance weights to expand, the distributor shaft rises up just enough so that the magnets don't line up with the pickup.

Eureeka! I put a washer under the pickup plate to make it a little higher and now it runs like a champ, up to 5,000 RPM no problem. Now I just have to get to the river for a test run!

Thanks for everyone's input on the issue. I'll report back after my test run, but looks like I finally figured it out.