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Hard start when hot

1K views 7 replies 6 participants last post by  obnoxus 
#1 ·
454 mpi with B&M blowers, Motors start well and now idle well with no stalling. But the starboard motor won't start after it sits for approximately 1/2 hr. without a lot of coaxing. When it does start you have to rev it until it settles in and then idles fine. The port motor starts fine everytime. If you turn motor off and then restart right away it starts fine. Any help out there?
 
#2 ·
whats your timing like? to much advance can cause hard cranking starts after warm-up? just an idea .... my small block would fire right up everytime first time starting but would be real ignorant after she got warm.... found that the timing was to far in advance, corrected it and have had no problem since...
 
#4 ·
Timing is ok, checked it, and called engine builder and it's right where it should be. I thought of possible vapor lock but you would think both motors would do it wouldn't you? Just got off of phone with FAST computer tech he says the after start enrichment table has to be come in quicker, told me because it's firing immediately but won't stay running it's starting on fuel start table, and not getting to after start table quick enough. He called it heat soaking. Sound right? anybody?
 
#5 ·
I think that's very similar to the vapor lock syndrome. Heat from engine is heating fuel while you sit. That's why it's hard to start after it's been warmed. I know Merc had a cool fuel system(recirculates fuel back to tank ? I think) that was supposed eliminate this problem but I know of some people who still have the problem even with cool fuel system ???!!!

I'm not sure why one engine would work and one not ? Do they both run about same temp ? Is there any different routing of fuel lines ?

I'm just throwing ideas out.

Good Luck keep us posted.
 
#6 ·
the merc vapor lock problem was mostly with the VST system, and the port engine was the worst, because the fuel filter for that side was in a high heat area, merc's idea was the cool fuel, it helped but some still had problems, also gas is a big part of it, its called reed vapor pressure, the higher the octane you run can help out on this problem also[ slower burn] also summer grade and winter grade play a role on this, and quality of fuel, are these the B&M 250 blowers that have the upper part of the mpi intake made on the bottom? you unbolt the mpi upper and bolt this blower/intake onto the lower factory intake? if so what year do you have? are you running MEFI1 ecm, are MEFI3?
Mark
 
#7 ·
FIRST HOW OLD ARE YOUR SEA PUMPS? IF THEY ARE OLD YOU MAY BE EXPERIENCING THAT THE WATER IN YOUR ENGINE WHEN SHUT OFF IS DRAINING DOWN BECAUSE OF THE CLEARANCE BETWEEN THE IMPELLER AND THE HOUSING. THIS WILL INTURN CAUSE THE HOT WATER FROM THE BLOCK AND MANIFOLDS TO DRAIN BACK SLOWLY AND SUPERHEAT THE FUEL. THIS WILL INTURN VAPORIZE THE FUEL. THE VST AND THE COOL FUEL PUMP AREN'T GOOD SUCTION PUMPS ESPECIALLY WHEN THE FUEL IS VAPORIZED. IF YOU HAVE THIS PROBLEM ,YOU CAN UNSCREW THE FUEL FILTER(SEPARATER) AND THE FUEL IN THE FILTER WILL BE DOWN AN EIGHTH OR QUARTER OF AN INCH. YOU CAN INSTALL A PUSHER PUMP OR REPLACE YOUR WORN SEA PUMPS. THIS WILL SOLVE YOUR PROBLEM. MIKE
 
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