1999 7.4 won't start

[Dark Horse]

Hey all
I have a 1999 270 DA with a 7.4 mpi. I recently acquired this but do know it wasn't started for quite some time. I have been going thru replacing the various obvious things but when I tried to start it, the motor cranks and almost starts. its got spark and fuel pressure at the Schrader valve. I'm thinking possibly the injectors are clogged or bad.
What else could it be?

 

[370Dancer]

Hey all
I have a 1999 270 DA with a 7.4 mpi. I recently acquired this but do know it wasn't started for quite some time. I have been going thru replacing the various obvious things but when I tried to start it, the motor cranks and almost starts. its got spark and fuel pressure at the Schrader valve. I'm thinking possibly the injectors are clogged or bad.
What else could it be?

Did you replace the fuel water separator? I've had fuel evaporate to the point that it's like vapor lock.
fuel pressure is 37-42 lbs? does it hold? I wouldn't start at the injectors. Try a portable tank with brand new gas in it. Do not mix new gas with old, you will wind up with spoiled new gas.

 

[Dark Horse]

I replaced the fuel filter with a new one and filled it with fresh gas. Took hose off tank and had a one gallon tank with fresh gas that it was feeding from. I don't trust the gas in the main tank and will pump that out and start fro m new later one.
I just wanted it to start and while it almost does it seems gas starved which is why I'm think injectors. Also check the distributor and confirmed timing and firing order were set and correct.

 

[Dark Horse]

Not sure about fuel pressure but when the Schrader valve is depressed gas shoots out.
Pump runs when key is turned for like 5 seconds and then runs again while cranking.

 

[boatrboy]

Try giving it some throttle - say 1/2 way, if it starts then stalls at idle, it’s probably the IAC. Be ready to back off the throttles as soon as it starts (if it does) so you don’t over rev it.
I had the same boat and every year in the spring when I “summarized” it it was hard starting. I often had to keep throttle open until one year I replaced IAC and it was fine after that.

After that there are some many things to look at. Was it running when you put it away, etc….

 

[Dark Horse]

Have tried pushing throttle up. Same exact symptoms. Almost starts on a few cylinders but won't continue on.
Never had it running as I inherited this. It onky has 284 hours on boat , was a one owner before me. At this point it seems like it may be injectors as i would think if it was anything electrical it wouldn't almost fire nor have a good spark (which it does)

 

[370Dancer]

Fuel pressure gauge would be more accurate.

 

[Dark Horse]

Don't have a fuel pressure guage. Will need to buy or rent one. Then if fuel pressure is good, on to pulling injectors.

 

[hottoddie]

Replace the distributor cap and rotor. The spark can jump from one terminal to the next and prevent the engine from starting.

 

[Pirate Lady]

Ask my wife. She has the answer for everything. How I drive the car, the boat, how I start the boat. cant get the btch to help with lines, but she sure has strong opinions about everything concerning the boat and why I doing everything wrong.
She wants to retire end of year, She'll be dead by March.

 

[bfernald0]

Does it have compression?

 

[Dark Horse]

It has good compression. I have ordered a fuel pressure gauge and once I get that reading I'll report back here and then go from that point

 

[El Capitan]

Here's what I did after long lay up.
Replaced original fuel pump from 1981
Replaced carb, PO installed an automotive Rochester, I installed a mercruiser Rochester
Drained all old fuel
Replaced fuel filter/water separator

Started right up and runs like bat of of hell. Last thing is to adjust accelerator pump on carb to eliminate minor bog when flooring it.

There are no short cuts. These things are so often fuel related issues.

 

[Dark Horse]

If only it had a carb. My 71 SS has the 454 with a carb and I can rebuild that one blindfolded.
This is MPI and a little harder to diagnose but I am still leaning towards the fuel injectors being all crudded up as the ethical gas does quite a number on them and people are inherently cheap when it comes to fuel.

 

[Dark Horse]

Okay got the fuel pressure gauge on it. Turn on key, pump runs for a couple seconds. Guage reads 20 psi. Tried to start engine -same reading.
Took guage off, release residual pressure from fuel rail. Started all over again with pressure guage -same result.
So it needs a new fuel pump.
Anyone re place these pumps that are part of the "cool fuel" system? How hard of a job?
Not afraid of the work just never done one of these.

 

[370Dancer]

Okay got the fuel pressure gauge on it. Turn on key, pump runs for a couple seconds. Guage reads 20 psi. Tried to start engine -same reading.
Took guage off, release residual pressure from fuel rail. Started all over again with pressure guage -same result.
So it needs a new fuel pump.
Anyone re place these pumps that are part of the "cool fuel" system? How hard of a job?
Not afraid of the work just never done one of these.

Hard part is getting the cool fuel system out so you can work on it on a bench. Hopefully you have pretty good access to it. You'll remove the line from the fuel water separator, and the return line (I just pull them with the cool fuel module), the high pressure fuel line up to the fuel rail, the vacuum hose to the regulator, and the raw water hoses from the cooler. Disconnect the power cable to the pump, remove the 2 nuts or bolts holding the bracket onto the engine mount, and it should slide right out. Stringers can get in the way. I don't know your boat, so I can't help there.
The pump is pretty straight forward. Look for debris in the inlet filter screen before changing it out. Good luck

 

[370Dancer]

Hard part is getting the cool fuel system out so you can work on it on a bench. Hopefully you have pretty good access to it. You'll remove the line from the fuel water separator, and the return line (I just pull them with the cool fuel module), the high pressure fuel line up to the fuel rail, the vacuum hose to the regulator, and the raw water hoses from the cooler. Disconnect the power cable to the pump, remove the 2 nuts or bolts holding the bracket onto the engine mount, and it should slide right out. Stringers can get in the way. I don't know your boat, so I can't help there.
The pump is pretty straight forward. Look for debris in the inlet filter screen before changing it out. Good luck

TIP: mark the orientation of the inlet and return line connectors so they have the correct bend when putting them back on. It's tight.

 

[boatrboy]

Okay got the fuel pressure gauge on it. Turn on key, pump runs for a couple seconds. Guage reads 20 psi. Tried to start engine -same reading.
Took guage off, release residual pressure from fuel rail. Started all over again with pressure guage -same result.
So it needs a new fuel pump.
Anyone re place these pumps that are part of the "cool fuel" system? How hard of a job?
Not afraid of the work just never done one of these.

Its not that hard - I did it several times. I would disconnect the fuel lines and pull the whole unit out and swap it on the bench. If I remember correctly I unbolted the mounting bracket from the motor mount bolts (studs) and pulled the unit out. The black plastic cover snaps pull if you pull gently from the bottom and pivot up. The upper right in my picture has a shoulder bolt and o-ring which holds the fuel line in place here. I don't remember the left side - but you will see it.