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| Cris craft Commander 31 Engine Trouble |
| Author |
Message |
    
Dick Schouten
Member
Username: robin_schouten
Post Number: 4
Registered: 07-2009
| | Posted on Saturday, August 01, 2009 - 01:52 pm: | 
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I recently own a Chris Craft Commander 31 (form approximately 1974) with 2 PCM Chevrolet 305 Engines new installed in approximately 1992.
The left engine works fine but the right engine backfires and dies with more than appr.1400 RPM under load. And I cannot make this engine run OK
Since then I have had the Holley carb.completely rebuild. Put in new ignition points + rotor + condenser + cap + spark plugs + coil.
Set the points with a dwell meter on 28 degrees (works better for me than a feeler gauge) and timing 9 degrees BTDC (as in the manual) on flywheel with strobe scope .
The (cold) engine starts immediately runs perfectly smooth on idle but under load it holds back enormously
when I go over 1400 RPM throttle. (no more backfires after working on the ignition)
If I quickly reduce throttle (under 1000 RPM) the engine will return to normal if i keep the same or higher throttle the engine dies completely
I have checked the ignition (with the strobe scope lamp) and the plugs are still firing when the engine dies
I also mounted the carb. from the good working engine and the problem was still the same. (so rebuild carb. is good).
There is a clear tube on the fuel pump but there is no fuel in it so I think this is working ok..... Could be broken....
I bypassed the fuelsystem by using a small fueltank straight onto the fuelpump. No difference.
I still think that it is a fuel problem but I don't know what to do anymore.
The last thing i can think off is swapping the pump from the other engine or measuring the fuel pressure of the pump.
Does anyone have any other suggestions for me? |
Dave Bullington
Member
Username: dcbullington
Post Number: 9
Registered: 09-2008
| | Posted on Monday, August 17, 2009 - 08:27 pm: |
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It sounds like you have it isolated to the fuel pump for sure. You can either:
1) replace the fuel pump (either swap from the other engine or just buy another one) or
2) hook up an external, electric fuel pump and see if that fixes it.
Dave |
Lee Bradshaw
Member
Username: lbradsha
Post Number: 24
Registered: 05-2007
| | Posted on Friday, August 21, 2009 - 09:48 pm: |
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Dick,
So you know.. I have a 72 33' COHO twin 350's.
I had the same type of problem with mine.
My fix was to turn off all of the fuel valves (i. e. All of them) select a fuel supply line ( I chose the generator line) and set up a electric fuel pump to a pressure regulator and "Y" union to feed both engines ....
The trick is to put a goldenrod filter before the fuel pump. And mount it securely very securely..
My problems was varnish from one tank.. But now I see the varnish gathering as a white crystal in the filter and can change it. It keeps the water out and I can see the fuel flow.
Just something to think about, there's more that one way to do just about any task.. pick the one you like best and go that way.
I have had the fuel pumps rebuild, and when the varnish gets down to a level I can live with I put them back in and go that way.
I have pictures and part numbers if it helps?
best of luck
Lee |
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