Timing or Carburated Issues?????

[dobler5]

Hey guys, I hope you can help me out on this problem.

Heres my problem: I can run around the lake at 3,000 RPMS ALL DAY long without a problem. (after running, turn the motor off and look in my carb. with the throttle completely open so the carb. is open and white smoke comes back out of it)

BUT: The moment I open my throttle all the way, which is about 4200 RPMS, it'll only go good for the max 5 mins. It will lose power and shut down. (Once again white smoke comes back out of the carb. with a gassy smell as well)

What is my problem? Carb..or timing issure?? PLEASE HELP!

I have a 1991 OMC Cobra v6 4.3L 2bbl

ALSO: Can anyone tell me what exactly is the point of a power pack!? Do they go bad?

THANKS FOR YOUR TIME AND HELP!

 

[dobler5]

Re: Timing or Carburated Issues?????

Any Thoughts?

 

[zbnutcase]

Re: Timing or Carburated Issues?????

Fuel supply issue. Start at the pick-up tube in the tank and go from there...

 

[whitney]

Re: Timing or Carburated Issues?????

Hi, I chased similar issues on an OMC 4.3. Couple of points:

- White smoke coming out of throttle is not an issue, it's just leftover atomized fuel

- Power pack I believe is an electronic ignition system used on newer motors. I believe a 91 had prestolite BID electronic pickup in a regular looking distributor (I have the same system on a '92)

- Definitely sounds like a fuel delivery problem, but could possibly be a failing ignition system too. But do check fuel first.

- I highly recommend plumbing a mechanical fuel pressure gauge into the line from the fuel pump to carb and watch fuel pressure during your running problems. This will positively rule in or out fuel and is easier than tearing everything apart, unless you want to do that anyways.

 

[HT32BSX115]

Re: Timing or Carburated Issues?????

ALSO: Can anyone tell me what exactly is the point of a power pack!? Do they go bad?

If by power pack you mean the ignition module for your 91 OMC. (Spitfire ignition OMC#986853)

They probably do go bad.....everything does..... With that part though, I think you'll be "done". It appears they're not available anymore.

Depending on your model engine/drive, part numbers can be found here: http://epc.brp.com/

Regards,


Rick

 

[BAproject]

Re: Timing or Carburated Issues?????

White smoke from the Carb is normal....dying at WOT, however, is not.

I assume on the '91 it's a mechanical fuel pump. have you replace the filters/gaskets, etc....chase down the entire fuel line and look for obstructions. Might need a carb. rebuild as well. At normal running speeds the bowl in the carb can probably keep a fuel supply, but when you start upping the RPM then the bowl obviously drains much faster and whatever obstruction or supply malfunction is happening will make the bowl basically go dry...hence....the problem

 

[Bondo]

Re: Timing or Carburated Issues?????

Ayuh,... Sounds like Fuel delivery to Me,... Change the Fuel Filter....

 

[dobler5]

Re: Timing or Carburated Issues?????

I have a newly rebuilt carb. in it. I replaced fuel filter already. I do have a mechanical fuel pump in it still. Do you really think this is my problem? I dont wanna spend alot of money on an electric fuel pump and than that is not my problem.

So white smoke coming back out of my carb. is completely normal and ok? That has nothing to do with timing issues?

 

[dobler5]

Re: Timing or Carburated Issues?????

And sorry about this but its not the power pack....its the shift assist module/ what is the whole purpose of this?

 

[dubs283]

Re: Timing or Carburated Issues?????

check fuel pressure and vacuum while running the engine at the rpm's you are having the problem at, this will tell you if the pump is bad and/or have a blockage or supply issue in the fuel tank

you don't need to replace with an electric fuel pump, they still make mechanical pumps

and you don't have to spend a lot of money throwing parts at it if you troubleshoot and identify the issue

 

[dobler5]

Re: Timing or Carburated Issues?????

How do I test the fuel pressure? Only have a problem at full throttle...What do i need to do to test this?

 

[whitney]

Re: Timing or Carburated Issues?????

How do I test the fuel pressure? Only have a problem at full throttle...What do i need to do to test this?

If you have a hard line connecting the pump to the carb like I do, this is what you need:

- Remove hard line
- Buy a few feet of marine 5/16" fuel hose (auto will be OK for limited testing but you will be illegal)
- Buy two 5/16" hose barbs from auto parts store (match the thread on hard line, it's for flared fittings)
- Get yellow teflon tape from HD/Lowes and use on all threads
- Get two 5/16" hose barbs with 3/8" pipe thread from HD/Lowe
- Get one 1/4" hose barb with 3/8" pipe thread from HD/Lowe
- Get a 3/8 pipe thread tee
- Get several feet of 1/4" marine fuel hose (auto OK again for limited use)
- Get a vac/pressure gauge from auto store
- Assemble and use good hose clamps. Tee the gauge into the line and put somewhere that you can see it safely when running WOT. Pressure test everything on muffs in the driveway and be DAMN SURE that there are no leaks.

Good luck! I just did this, it's not as bad as it sounds if you've assembled hose fittings before.

 

[6meter]

Re: Timing or Carburated Issues?????

First of all, running at WOT for 5 minutes isn't healthy for any component in the back. However, right after it dies, does any fuel squirt in the carb when you pump it? Is there voltage at the + side of the coil? Those answers will tell you if you have an ignition or fuel problem. Timing dosen't seem to be the issue. Carb "smoke" is normal.