2005 Optimax 75hp help please

Brad750

Cadet
Joined
Jul 8, 2011
Messages
6
Can anyone tell me what pressure I should be getting from the boost pump? I have 80 psi air and 90 psi fuel high pressure (on the rail). But I am only getting around 5 or 6 psi from the Schroeder valve on the bottom of the vst down by the return line. This thing runs for about 3-4 minutes just fine then dies like its running out of fuel. Ive searched the forums for a few days and checked everything on here.
1: Ran on external tank
2: rebuilt pulse pump
3: took VST apart and checked both pumps in a bucket of fuel.
4: New filters

I even went as far as disassembling the front of the motor to check the reeds which all were perfect.

Im lost.
 

Brad750

Cadet
Joined
Jul 8, 2011
Messages
6
Thank you VERY much AllDodge!!

Looks like I've got low psi on that booster pump.
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
43,398
Could be, I'm not an OB guy, just tossing some ideas. Even with low pressure I would think it would run at low speeds with lower then normal pressure. They say to check the vacuum going to the transfer pump and it should not be more then 2 in Hg from the anti siphon valve (or at least I think that was the number)

Hope you find the issue
 

Brad750

Cadet
Joined
Jul 8, 2011
Messages
6
Well after trying to troubleshoot this unique fuel system I decided to purchase a boost pump as a guess. Ill report back when I get it installed.
 
Top