'95 SN starting problem

My '95 Sport Nautique, multi-port injected engine is beginning to exhibit starting problems, i.e. it fires immediately but then coughs and quits. It's like whatever supplies fuel just after starting doesn't always kick in and it dies.. It only happens once in a while but it seems to be getting worse.

From what I can see my Pro Boss, '95 GT 40 engine does not have a Fuel Control Cell as the fuel comes from the tank to the low pressure pump and then goes directly into the high pressure pump. Does this sound correct?

My fuel pump relay must not be bad because I hear the fuel pump come on for a few seconds each time I turn the key to start.

I see a simple rubber (Neoprene?) hose coming out of one of the modules that has a water tight electrical connector. That hose runs through the distributor boot and then into a whiteish plastic cylinder that looks a little like an inline fuel filter, which I don't think it is.

I'm thinking my problem must be the low and/or high pressure fuel pump. I see that part still listed on Nautiqueparts.com as PN: RA080025A...is it still available? The low pressure pump is listed there as well, PN: RA080018.

As I stated earlier my engine runs absolutely perfectly 99% of the time but sometimes it will crank just fine and fire but whatever is supposed to keep[ the fuel flowing to keep it running just doesn't catch hold.

Make sure both electric pumps come on with the Key. It will take two people because the pump will come on as you turn the key and shut off 3 seconds later.
It will do this every time you turn the key but will only stay on if the engine starts.
This is a safety feature built in.
Verify your fuel pressure at the fuel rail Schroeder valve.
If the low pressure pump is coming on and the fuel pressure is low the problem is at your high pressure pump.

Thank you for chiming in on this problem. I've read many posts on this topic and gained some good understanding.

I don't know if either of the fuel pumps have been replaced as this is just our second summer owning this boat.

I disconnected the HPP electrical connection and when I turn the ignition on the LPP makes a noise like it's working. I reconnected the HPP electrics and disconnected a wire to the LPP and the HPP also sounds like it's working but makes a higher pitch sound.

It makes sense that they both work as the engine runs flawlessly 99% of the time.

It kind of seems that it may be an intermittent vapor lock when the engine is warm.

I'll test that theory tomorrow although I doubt it will act up when I want it to on any consistent basis.

I guess I should get a fuel pressure gauge at Harbor Freight and have it handy for the next time the problem occurrs.

Thanks for the help so far.

Should I try disconnection the second steel braided line from the bottom of the HPP and plugging it as I think I read in a post?

Drop a quart of Automatic Transmission fluid in the fuel tank with at least a 1/2 tank of gas. It helps lubricate and clean the pump and injectors. Not legal to use in a car with a catalytic converter but works great in a F.I. boat.   You will not detect even a puff of smoke but it does lubricate well.
Run the engine normally.
The next time it stalls or won't start take a rubber hammer and tap on the low pressure pump. If fuel dries out in the pump as it can do over the winter months it leaves crusty particles behind. They can interfere with the pump rotation. Sometimes a little tap can break it up and make it run fine. I am not suggesting a hammer swing like you drive a nail with, just a couple bumps. Option 2 is pull the low pressure pump apart and inspect it. Sometimes there are particles you can remove. The LPP is a very durable design, it just does not function well if particles have accumulated in the vanes.   I have not pulled a Carter Marine pump apart and they may have it sealed but I have taken apart the Carter automotive pumps that look just like the Marine pump.
These are fuel lubricated pumps and don't do well if the fuel dries out in the pump. The LPP has a cavity that does not drain in the bottom of the pump where the electric motor is housed.. Perfect spot for fuel to evaporate over the winter leaving the crud behind.
Most Motorhomes prior to fuel injection ran this low pressure Carter pump and I saw this many times in Motor Homes that sat a period without use.
If this does not fix it the LPP is less than $100.

a flow test on the lpp might be a good Idea. mine turned, but didn't pump fuel at one point.   Sounds like Mark's theory might have been the demise of my LPP.

Paul,gundriver here on the site has done just that with his. we will have to see what parts he used.

I agree with Gun=driver, test the fuel pressure at the schrader valve on the injector fuel rail when it will not start. You should see about 40 psi.

What I found on mine was air in the line. I believe the air was from the first couple cranks of the engine the injectors using the fuel in the rail and the fuel pump failing to keep pressure at 39psi +/- 3.
What I did when it wouldn't start was attach the tester and jump the pumps to run continuously then use the bleed function of the tester to bleed the line of air into a bottle (usually Molson Canadian...yum ) and the motor would start and run fine.
This is the tester I use
https://shop.advanceautoparts.com/p/actron-fuel-pressure-tester-kit-cp7818/9030328-p?c3ch=PLA&c3nid=9030328-P&c3apidt=22084223098&gclid=EAIaIQobChMIo8Wtju311AIVj5x-Ch2upQ8bEAQYAiABEgI4EfD_BwE&gclsrc=aw.ds

In addition, with the engine at idle the PSI jumps from 32 to about 38 when I remove the vacuum line to the fuel pressure regulator and goes back to 32 when I re-connect it..

420 hours. I suspect the LLP has been replaced even though it is black on the outside on the easiest to see surface. Upon careful inspection I can see that the main, sort of canister, part is bright metal where it's not easy to see. The guy I bought this boat from was a detailing freak and he, very carefully, painted everything black to keep it new looking.

I'm going to keep the fuel pressure gauge attached for the foreseeable future and hope the hard starting problem will rear its ugly head and I will be able to see some explanation in the fuel pressure.

I have a new LLP and fuel filter on hand and I was going to replace them when someone on this thread suggested checking the pressure at the fuel rail before buying a bunch of new parts. I sure wish, #1. the hard starting problem would occur while I have the pressure gauge connected and, #2. I could, once and for all, determine what causes the random, occasional hard starting problem from what the fuel pressure gauge tells me.

It sure seems like it might be some kind of a vapor lock problem.

When trying to diagnose a problem/symptom its best to understand or at least some what understand how said system works!!!
As I posted before, there is a very good manual in the reference section that would help you understand what your gauge is telling you.
http://www.correctcraftfan.com/Downloads/Pro_BOss_GT-40_Service_Manual.pdf
I would read section 2B

Sounds to me that your pressure regulator is working and one of your pumps is getting weak.
When you first turn on the key you should have a solid 39+/- 3 psi you shouldn't have to continue to cycle the key to boost the pressure.
I would check the screen in the bottom of the HP pump for restrictions, then check the fuel flow/pressure from the LP if that all checks out its probably the HP.

1xsculler wrote: Another thing I'm going to try is to push the purge, or pressure release, button if the problem recurs in hopes of relieving any fuel rail vapor lock.

The Schrader valve?

If it acts like mine did at the end it will take a little while to clear the rail and the pump to catch a prime, should jump the pumps so they run continuous. You will hear the pump change tone when it primes be prepared to catch the fuel in something as you will get several ounces out of the line.