Shraeder valve? Bleeding air from fuel lines?

[geekeasy]

I just got a Silverton 312 from 1996 with twin Marine Power 5.7s. It was sitting for a few years and I'm trying to get it running. I don't know much about this sort of engine, but I'm learning quick.

I manually emptied the fuel tanks of the old bad gas. I replaced the fuel filters and fuel/water separators. The engines won't start. I checked the fuel filter and the fuel/water separator and they were both totally dry.

I filled the filters with fuel, and the starboard engine started right up and ran for a minute before dying. I'm not sure if the fuel pumps are dead or if it's just failing to pull fuel because there is too much air in the system.

How can I bleed the air out of the fuel lines on these engines? And is there a shraeder valve somewhere that I couldn't find to check fuel pressure?

Thank you for any help!

 

[makomark]

most of the SBC made in 96 came with the TBI flavor of fuel injection...GM's TBI has no shraeder valve for pressure checking...

The systems are 'self bleeding'...and they underwent a lot of changes in the early years of using EFIs in the marine world...

The Fuel pumps are typically 12VDC supplied and are controlled by the ECU thru a relay...you can pull the relay and jump its socket for troubleshooting purposes...also a good idea to replace the anti-syphon valves and inspect all of the rubber hoses...also, make sure the shut-off valves are open...

 

[geekeasy]

Thanks a lot for the help!

The systems are 'self bleeding'...and they underwent a lot of changes in the early years of using EFIs in the marine world...

Should this "self-bleeding" happen when I turn the key to the "on" position. I can certainly hear the pumps activate when I turn the key. Or do I need to keep turning over the engine to try to bleed it?

The Fuel pumps are typically 12VDC supplied and are controlled by the ECU thru a relay...you can pull the relay and jump its socket for troubleshooting purposes...

Can you tell me more? Is that just the two plugs on the bottom of the pump?

also a good idea to replace the anti-syphon valves and inspect all of the rubber hoses...also, make sure the shut-off valves are open...

Someone else suggested that this problem could likely be the anti-siphon valves. But I opened up the fittings at the top of the tank and there didn't seem to be any anti-siphon valves at all. Is it possible that they were never installed or someone removed them?

 

[makomark]

Self bleeding - yes and no... The pumps will typically run for 2 seconds when the key is turned on...this usually isn't enough to fill and pressurize the system after major servicing...unless repeated for many key cycles. and that assumes the relay and the pump are working...does the pump run continuously with the key on or only for the <nominal> 2 sec prime cycle?

Get you owners manual or the sevice manual online...find the relay and then remove it from the socket. take a jumper and connect between the +12VDC feed to the relay and the supply wire to the fuel pump...the pump should turn on if the 12VDC feed is active. (some have a separate fuse for the fuel pump, before the relay...

the fuel pumps typically have a quick connect connecto for the DC power supply leads...they are usually on a short wire pigtail exiting the pump.

On the anti-syphon Valves - i'd say a lot depends upon your assumptions regarding their appearance...many will look very similar to a hose barb adapter. as far as them being removed, anything is possible, espeicially if you bought the boat used.

 

[geekeasy]

Again, super useful. Thanks!

The pumps run for 2 seconds then stop. I'll try to jump it and see if I can pressurize the system.

Is there any convenient way to know if and when fuel has flowed through it? Or just run it for say 2 minutes and then see if the engine starts?

 

[makomark]

fuel flowing...good question... I would say one minute is enough to fill the system...you may be able to hear a change in the pump's speed as the pressure builds...the TBI's usually don't need more than 20 PSI to work so its not always easy to hear the pump change...

another item that may help is to do a www search for DELPHI MEFI-1 manual...most everybody uses the default GM provided data for their (factoy) service data...I even think Marine Power has them posted on their www site...the Delphi manuals are the best one-stop data source for everything the ECU controls.

 

[geekeasy]

Well.... it's been a learning process:

1) Jumped the wires on the fuel pump and ran it for 2 minutes. No luck.

2) With some difficulty due to the lack of access managed to break free a fuel line. Couldn't find the right fitting so I rescue taped a portable fuel transfer pump onto the line.

3) The fuel transfer pump was pulling almost no fuel; just pulling air.

4) I thought it might be an issue with the tank being too low (only 20 gallons), so I half filled a 55 gallon drum of water on the port side to heel the boat over and move the fuel toward the intakes.

5) Now the fuel transfer pump pulls fuel at a decent rate.

6) Reassemble the fuel hose and after a few seconds of cranking the starboard engine starts up.

I'm going to go and pick up another 15-20 gallons of fuel and then work on the port engine.

 

[makomark]

may be time for a new pickup tube...??? either that one is cracked (or damaged) or was cut too short when installed....