540 BBC running poorly
11-12-2018 | 08:37 PM
#71
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From: chicago
I personally would ditch the electric pump/mechanical setup. Id run one or the other.
those holley red pumps are crap. Id get rid of it. They dont flow worth a dam ,and if anything are probably a restriction in the setup. They barely support 400/425hp . Then you have tee's , filter restrctions, etc.
id get a decent mechanical pump, run a -8 line from tank to pump, and -8 to carb feed line. Id also make sure the carb has at least .110 needle and seats.
i wouldnt be surprised if youre starving those engines for fuel.
those holley red pumps are crap. Id get rid of it. They dont flow worth a dam ,and if anything are probably a restriction in the setup. They barely support 400/425hp . Then you have tee's , filter restrctions, etc.
id get a decent mechanical pump, run a -8 line from tank to pump, and -8 to carb feed line. Id also make sure the carb has at least .110 needle and seats.
i wouldnt be surprised if youre starving those engines for fuel.
11-12-2018 | 09:20 PM
#72
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From: NW Michigan
All the years I've been messing around with all sorts of different engines I've never ran an electric in line to the mechanical pump. I may have missed somewhere but did we confirm the electrics pumps are even working at all? I could see that being a real issue with flow and holding pressure. I mentioned earlier fuel pressure at WOT and I recal OT checking with both gauges. Are they within view at WOT?
I forgot ign boxes were sent out and checked and came back with a clean bill of health. I'd still no throw out ign all together. It seems if there might be a combination of things however maybe not. If Engine isn't on its ignition, timing game it can certainly act like its starving for fuel also. OT can you here it suckin air and almost like balding down while into the secondaries.
I agree with joe for sure on the fuel plumbing, pumps etc. The boat was purchased with these engines and off 1,500 from day one. Red flag!!! Doesn't mean anything at this point I get it but... gotta move forward and figure it out.
I forgot ign boxes were sent out and checked and came back with a clean bill of health. I'd still no throw out ign all together. It seems if there might be a combination of things however maybe not. If Engine isn't on its ignition, timing game it can certainly act like its starving for fuel also. OT can you here it suckin air and almost like balding down while into the secondaries.
I agree with joe for sure on the fuel plumbing, pumps etc. The boat was purchased with these engines and off 1,500 from day one. Red flag!!! Doesn't mean anything at this point I get it but... gotta move forward and figure it out.
11-13-2018 | 03:09 AM
#73
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From: Merritt Island, FL
I also thought the mech/elec fuel pump setup was odd. Maybe I rerigged that wrong when I put the engines back in?
My fuel pressure gauges are brand-new autometer electric gauges, the sender picks up at the end of the fuel rail after the carbs are fed, and reads 6-7 psi at WOT. Does this rule out the fuel pump setup being the problem?
Worth noting is that both Holley red elec pumps are less than 10 hours old, I replaced one over the summer and the other one about a month ago. The old pumps had corroded and seized about 2 months apart from each other. One, before I pulled the engines, the other, shortly thereafter.
My fuel pressure gauges are brand-new autometer electric gauges, the sender picks up at the end of the fuel rail after the carbs are fed, and reads 6-7 psi at WOT. Does this rule out the fuel pump setup being the problem?
Worth noting is that both Holley red elec pumps are less than 10 hours old, I replaced one over the summer and the other one about a month ago. The old pumps had corroded and seized about 2 months apart from each other. One, before I pulled the engines, the other, shortly thereafter.
Last edited by ancho; 11-13-2018 at 03:21 AM.
11-13-2018 | 05:59 AM
#74
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From: Merritt Island, FL
In the second pic, you can see the Tee fitting. The electric pump outputs to one side of the Tee, the center of the Tee is screwed into the INlet of the mechanical pump, and the other side of the Tee runs up to the carburetor. The outlet of the mechanical pump runs back towards the forward bulkhead, back to the fuel filter head, presumably as a return?
Last edited by ancho; 11-13-2018 at 08:33 AM.
11-13-2018 | 09:01 AM
#76
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From: Paducah, Ky
That's a very odd setup to me, you might have 6-7 PSI at WOT but more than likely you don't have adequate fuel flow due to the Mech/Electric pump setup. It appears to me that the mechanical pump is robbing fuel flow from the carb and sending it back to the filter head.
Last edited by Jim Diesel; 11-13-2018 at 09:13 AM.
11-13-2018 | 09:47 AM
#78
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From: Merritt Island, FL
11-13-2018 | 11:52 AM
#79
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From: Paducah, Ky
Correct, the SSM and TRS boats had a booster electric fuel pump that ran when the engine would crank and as long as the oil pressure was over 20 PSI. The Electric pump sent fuel to the fuel filter/separator, then to the Mechanical fuel pump, and from there to the carb.
