| Author |
Message |
    
Greg Bedrosian
New member
Username: hoss8666
Post Number: 1
Registered: 09-2009
| | Posted on Sunday, September 27, 2009 - 11:45 am: | 
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I have twin 318's in my 78 trojan and my left engine stalls after warn up when under a load. Had the same problem with my right engine but replacing fuel pump fixed it then it started with my left almost right away so I relaced that fuel pump but problem still occured. I was told that a good test for a fuel pump being bad is that you can blow air through the fuel inlet of the pump which I was able to do but I was also able to blow air through the inlet of the new pump as well. Is it possible I got a defective fuel pump? Does anyone know if that test really is a good indication of a failing pump? When I replaced the fuel pump on the other engine I wasn't able to blow air through either the inlet or the outlet of the new pump but could on the old one. |
David Gee
Member
Username: redpaint
Post Number: 4
Registered: 08-2009
| | Posted on Sunday, September 27, 2009 - 01:45 pm: |
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Greg I also have a F28. I can't answer the question about air through the pump. How old are your fuel filters ? Also I had bad fuel that cost me lots of time / stalling / poor idling |
Fastjeff
Senior Member
Username: fastjeff
Post Number: 6847
Registered: 09-2003
| | Posted on Monday, September 28, 2009 - 05:22 am: |
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The only real test of a fuel pump is pressure in run. Cap off the outlet and install a pressure gage. You should see about 4 to 6 psi.
Jeff
PS: I'm with David. Sounds like fuel starvation more than a fuel pump issue. |
Greg Bedrosian
New member
Username: hoss8666
Post Number: 2
Registered: 09-2009
| | Posted on Monday, September 28, 2009 - 09:04 am: |
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Thanks for the input guys. I have replace my filters multiple times this season and I dont see any signs of bad fuel, no water, no seperstion, nothing. The only thing I keep coming back to is the fact that no air could get through the fuel pump on the right engine and it get through the one on the left. |
PF Herzog
New member
Username: peter_h
Post Number: 3
Registered: 09-2009
| | Posted on Tuesday, September 29, 2009 - 09:02 am: |
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Greg:
I had a '77 Trojan with twin 318's and had both fuel pumps fail at about the same time. They were the older style pumps with the two rubber membranes. If that's what you have in your '78 do yourself a favor and replace it with a new style pump without those rubber membranes. Much safer. Make sure it's a marine fuel pump and run the overflow tubing to the carb. There are two versions, one has an off-set in the arm to accomodate a double timing chain. You need the pump with the straight arm. |
Fastjeff
Senior Member
Username: fastjeff
Post Number: 6873
Registered: 09-2003
| | Posted on Tuesday, September 29, 2009 - 09:24 am: |
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Hey, PF, not many people know about those two fuel pump types! I'm impressed. Here's a photo of the two. I believe the offset type will work in either case, but you must use the offset type with the double row timing chain setup.
Jeff
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Greg Bedrosian
New member
Username: hoss8666
Post Number: 3
Registered: 09-2009
| | Posted on Tuesday, September 29, 2009 - 05:13 pm: |
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Thanks guys, I did replace it with the one with the straight arm but was unaware about the rubber membranes. The only pumps I was able to find were from Sierra. They had the vent line to the carb just like my existing pumps. I went to West Marine today and asked them to pull another fuel pump off the shelf and I was able to blow air through that pump as well so I guess thats not a good test to see if a fuel pump is failing, I think the odds of them having 2 defective fuel pumps would be pretty slim. I'm starting to lean tward bad fuel causing my problem, I have a brand new carb on my right engine but this one is the original and has been rebuilt many times. The last time was about 5 years ago so it's probably due. |
