Old Merc 150 V6 without fuel enricher won't start

I have an older 150 v6 that has 3 dual barrel carbs. The motor will not start with out spraying fuel into the carbs. I rebuilt all carbs and replaced all needle valves, replaced all hoses and installed screw clamps, repaired the fuel pump, installed a fuel preasure gauge in the lower card fuel line, replace all hose to tank and installed a new squeeze bulb.
when I do get it started the fuel preasure runs 2-5 lbs. As soon as you shut the engine off preasure drops to zero. No amount of choking helps.

I understand mercs of the breed are famous for being hard to start and newer model have fuel enrichers that appear to just spray gas into the carbs before you turn the key.

I know I am missing something, they may be know to be hard to start but with proppert choke and throlle adjustment is should start.

Any thoughts?

Thanks

Re: Old Merc 150 V6 without fuel enricher won't start

When they get that old they loose some crankcase pressure thru the hard to start as it cant make carbs "flood" and what little is being introduced is being burnt. There are 2 this to look for, when cranking make sure voltage does not drop in circuit to make choke flaps crack open and the quickest way to start is a kill switch. Disconnect it,pump bulb, choke the chit out of it, install tether and start and go.

Re: Old Merc 150 V6 without fuel enricher won't start

Thanks for your response. The crankcase preasure makes a lot of sense. Voltage to chokes is good.

I don't know what you mean use kill switch to start it.

Thanks

Re: Old Merc 150 V6 without fuel enricher won't start

If it dont have one install one,then pull tether(no spark),pump bulb, choke the chit out of it, install tether and start and go.

Re: Old Merc 150 V6 without fuel enricher won't start

Got you, thanks, so if I have a reasonable crankcase preasure and pull the kill switch it will kinda work like an enricher. Makes sense I will give it a try.

Re: Old Merc 150 V6 without fuel enricher won't start

Thanks Faxbullet, Your suggestion worked perfectly.

Thanks

Re: Old Merc 150 V6 without fuel enricher won't start

Well Faxbullet it worked once. Since then I have had to spray mixed gas into cards to get it to start. Once I get it warmed up it starts pretty good.

Any other thoughts would be appreciated.

Re: Old Merc 150 V6 without fuel enricher won't start

one 115 inline 6 1983 could not start by mistake turned top of enrichen vale and it started. when I noted I could change idle by turning the pin on top of enrichen vale . small amount of gas seting in top of enrichen vale got new vale and now I can not ajust it and it's idleing hi over 1200RPM

Re: Old Merc 150 V6 without fuel enricher won't start

I just did an interesting experiment.

1st I confirmed that putting the palm of my hand over the inlet to the carborator I get an even suction from each barrel and my hand was wet with gas. This proves I have good vacum. I then started the motor ( i started the motor using point 2 below) and sprayed WD40 around the crankcase gasket and the engine didn't increase in RPM.

2nd I have a preasure gauge installed between the fuel pump outlet and and the lower carb. While cranking I got 2-3lbs preasure. Engine will not start without spraying gas into carbs. I had my wife choke and crank the engine as kept squeezing the gas bulb to build 10-15lbs preasure. The engine started better then it ever has.

What does this mean? Do I have leaking valves in the fuel pump?

Re: Old Merc 150 V6 without fuel enricher won't start

It sound like you are not getting fuel . check two see if you ajusted carb to a 1 and 1/2 turn and turn it to make carb are closed on start up

Re: Old Merc 150 V6 without fuel enricher won't start

This style of engine doesn't have adjustments on the carbs.

Re: Old Merc 150 V6 without fuel enricher won't start

Try this......

Pump bulb firm.
Trim ALL tha way IN or Down.
Hold choke in and crank it till it spits, sputters or in some way trys ta start.
Release key.
Raise fast idle just a touch.
Raise motor to level.
Turn key WITHOUT choke.
Repeat if necessary.

Unlike what some say, It takes a lot of fuel ta start tha older (and some newer) carburated Mercs. Its always worked for me on most.........

Re: Old Merc 150 V6 without fuel enricher won't start

sorry about card, ajustment I just got a mercury service manual for $5.00 and it is very helpful to me it dose show your engine and things you need to know if you don't have a service manual you can download it from tradebit.com and tryp in mercury it list some I got one for 1965to1989 from 70hp to150hp
good luck