View Full Version : What's my ProStar's problem???

06-20-2008, 03:33 PM
I need help diagnosing & fixing a problem on my 87 ProStar. It is my first MC & I bought it 2 summers ago. Last summer towards the end, I was low on gas but still pushed the engine hard. The next time I went out, the engine putted like it was about to fail any mintue & this was with a full tank of gas!!! I drove it a little to maybe clean out the fuel pump but it sounded like a 1930's ford that was just struggling all the way. Any attempt to give it more gas only created a stall and sometimes a backfire. My goal this weekend is to diagnose & repair. Does anyone have any troubleshooting tips or idea of what maybe the problem and what I can do to fix?



06-20-2008, 03:44 PM
What was done when it was put away for the winter? How long between filling the tank? When was the last tune up? What other problems has it experienced?

06-20-2008, 04:27 PM
Nothing... I just winterized it but it already had this problem before winter. Other than that, everything else runs good, and there have not been any other problems historically that I'm aware of. I believe it may need a new distributor cap (which I was planning to replace anyways) but that's it.

06-20-2008, 04:52 PM
I'd start with cap, rotor, plugs, wires if needed, points if it has them, fuel filter, and all the other normal tune up stuff. Is the fuel good? How long has the fuel sat, and with or with out stabilizer?

06-20-2008, 05:19 PM
Thanks flipper. I'll try all of those things. I have never put stabilizer in my tank, and I think the tank is probably pretty dirty. How would I go about cleaning it as well as the pump and/or gas lines?

06-20-2008, 05:33 PM
Pull it out, clean it really good, put it back in. For the lines, just flush them out, or replace them if there in that bad of shape.

06-20-2008, 06:17 PM
I would do a compression/cylinder leakdown test before anything else. If the tank was low and it was being run hard, it may have been damaged by being too lean. It could be that the carb is gunked up, so using a mustard bottle to drizzle some gas into the carb would let you know if it's being starved. The flame arrestor will need to come off for this and yo uneed to make sure to have a fire extinguisher handy, just in case.

While you're at it, clean the flame arrestor, PCV and look at the points, cap and rotor.

If you have a timing light and dwell meter, make sure the points and timing are correct. If the points aren't opening enough/long enough, it's going to run like a stove.

06-21-2008, 11:03 AM
id say its a fuel problem of some sort , most likley your carb is blocked up in one way or another but id also look at all the ignition components aswell just in case.

06-23-2008, 10:34 PM
Well... I spent all of Sunday getting the boat out of storage and diagnosing. I replaced the coil wire and the distributior cap (have old points system and thinking of moving to electrical) but I couldn't even start the thing because I my key was lost last summer but what able to use a different key to work with the tumblers. Now, I want to replace the key/ignition switch. Where do I go for that???? Is there a specific one I need? I tried one from a hardware store, but a slight turn of the key and the starter would trigger. Where do I go?

06-23-2008, 10:50 PM
You can get one here, http://www.skidim.com/prodinfo.asp?number=SIEMP39200 or maybe a MC dealer.

06-23-2008, 11:01 PM
Thanks! I'll give it a shot. My wire colors attached to the original was Purple - ignition, Yellow w/ red - accessory, & Orange to the Battery. I am hoping the 3 terminals on a new one will operate the same way.

06-23-2008, 11:22 PM
Thanks! I'll give it a shot. My wire colors attached to the original was Purple - ignition, Yellow w/ red - accessory, & Orange to the Battery. I am hoping the 3 terminals on a new one will operate the same way.

I would think the 3 position is correct, with acessory to the left, off in the center, right is run/crank!

06-25-2008, 03:48 PM
I'll be interested to learn what the problem turned out to be. You're on the right track so far. The problem is most likely electical. My neighbor has an '87 p/s and it had similar trouble stemming from a cracked (or leaky) distributor cap. His is a bit different than mine and has clips, rather than screws holiding it down IIRC. Seemed problematic. If you can get it started, you may have already fixed it.

Points may be worn. You'll need feeler gauges to adjust those. Rotor may be corroded. These are cheap parts and easily replaced.

I installed a Pertronix electronic ignition module in my boat 6 years ago and it's performed flawlessly. Not a moment's hesitation out of the hole with it. In my case, there was a ceramic ballast unit that had to be removed in addition to the standard installation instructions. Well worth doing.

07-01-2008, 04:18 PM
Thanks for everyone's help. I am ordering a 3 terminal ignition switch, electrical ignition system, & possibly a new coil. I'll keep you posted on the results.

07-04-2008, 12:35 PM
I'm not sure that's right. Don't you need 4 terminals? You have to have a terminal for power to the switch and then you need an accessory terminal, a run terminal and a crank terminal. If by three terminals you mean three 'output terminals' then that makes sense as your switch must have three different output positions, but there still has to be another terminal there to supply power to the switch.

Good luck !!


07-04-2008, 12:59 PM
I'm not sure why folks went immediately to electrical. You drove it low an gas, and now it sounds like you're not getting fuel. Before I tore into things, I'd ensure that the fuel system is clean. I'm thinking when you got down to the dregs in the tank, some junk in the tank got sucked in. I would start at the tank and make sure that the components of the fuel delivery system aren't gummed up- anti siphon valve, fuel line, fuel filter, fuel pump, and fuel line into the carb. Make sure everything is cleaned out and free of rust, dirt and other debris. My $.02. BKH

07-04-2008, 02:02 PM
"I'm not sure why folks went immediately to electrical."

I'm not, either and that's why my post (#7) includes what it does.

If it ran before, it should run now. Testing for fuel, spark, compression and timing don't take very long but it seems that a lot of people don't want to do that. Filling a cannon with parts and shooting them at the motor may fix it, eventually, but it's a slow, expensive process.

07-04-2008, 05:55 PM
Well today I installed a new electronic ignition kit and a new coil as well as a new switch but it seems that there is no current getting to the coil. The engine won't even fire when I turn the key. The starter is cranking but the coil is not creating any spark so I'm assuming that the resistor or something is blocking a current to the coil. The only problem is, I don't know where the resistor is or how it's impacting the coil. Any suggestions???

07-04-2008, 07:01 PM
Do your gauges move when you turn the key to ON? If not, look at the safety switch.
If necessary, connect the purple wire to a known live 12V source. That will at least get voltage to the coil.

07-05-2008, 01:59 AM
Thanks JimN and everyone else. I am happy to report that I successfully got my engine going on the 4th with the help of a 12V Coil thread I found on the site which had the missing link. I CANNOT STRESS ENOUGH how important it is if you are putting in an Electronic Ingition system into your distributor to make sure you BYPASS YOUR RESISTOR. This is specifically for a Ford PCM 351 engine on my 86' Prostar. I was very bummed earlier in the day after switching the points, installing a new switch, and replacing the coil, only to find I was not even receiving a spark from my new coil! I came back onto TCM talk and found a great diagram that said "EI Systems bypass ballast resistor". I went out to my boat, cut the connection to the resistor and spliced the purple ignition wires togeter, and within 2 minutes my boat was purring like a lion! What a great ending to a hard day's work...and on the 4th of July! Now, onto my next project - wiring my system for a new soundsystem with both in-boat speakers, tower speakers, an amp & sub!