Engine doesn't start without throttle opening

[Wave34]

2 years later, LOL.

I didn't had time to work to solve this problem until this summer.

To resume, the problem is hard start, after sitting for a while, (hours).
The first start is long to very long to no start and requires throttle.

Once it is started once, it fires well afterward, even only 10 seconds later like in my video. So that rules out all the sensors, bad distributor cap, spark plugs etc.

I changed the IAC, because of a bad diagnosis from me, and of course, it didn't change anything.

So, now, theory #1 is either there is carbon deposit behind the intake valve and it absorbs the fuel until saturated, then fuel can go into the cylinder.

Theory #2, there is a fuel pressure loss when the engine if turned off. Maybe some air gets sucked in the fuel rail and at the first start, the injectors are injecting air only.

NOTE: I removed my injectors and tested them one by one with a test rig I have that pressure it with fuel at 50 psi, and over a minute, not one drop could be seen on a towel paper.
I cleaned them anyways with a carb cleaner liquid injected with pressure and pulsing the solenoid.

In the video it takes time to start, but many times, it is up to 4X that time, and sometimes I need to give throttle.
All subsequent starts are fast, even the one after the 9 minutes of resting time and that the fuel pressure dropped down to 10 psi. That negates my theory #2, sort of...

When I left the boat yesterday, the fuel pressure was 50 psi, this morning it is at 0 psi, but the pump jumps it back to 50 in no time.

What do you guys think?

 

[alldodge]

Reading back thru it may be the IAC and I know you replaced it. I mean maybe its not working when first cranking. Remove the IAC when motor is cold and turn key ON, see if it retracts

 

[harveje]

My 04 5.0 gxi is doing the same thing but only on the lake starts great all the time on the hose. SO Safely get some 5/16 clear hose and replace the fuel vapor line on top of the fuel cell to the intake. Look for fuel, bubbles etc in the hose when pump spins up or when engine is running.. Mine after a long run and sitting for a few minutes I start to see and feel vapor pressure building up in my fuel cell and getting pushed into the intake causing what I think is my hot start / flooding issue. To verify this as soon as I shut down I pulled the hose off the intake fitting and could feel and hear the pressure at the end of the hose. I left the hose off, left the hatch open and ran the blower extra long, turned the key and engine fired right up, opposed to if I left the hose on I'd have to give it throttle to start. I've had my cell apart and check vacuum on that float assembly and it passed. I have another cell on the way and will swap them out this weekend and lake test it. If it passes I'll tear back into the cell to see what's going on.

 

[harveje]

Also, the high pressure pump has a check valve that may be stuck, and inside the cell there is some type of low pressure check valve that could stick too, along with the float needle not seating correctly.

 

[harveje]

If you want something fairly cheap to look at the codes and some parameters I use MEFI pro, it will read mefi 1-4 ecm's (i think), mines a -4, NOW it's not as good as a marine scanner but my budget at the time was slim..

 

[SD2600]

Another option would be to check your neutral safety switch in your throttle mech... I had a stiff shift cable that wouldn’t quite allow the switch to seat properly causing the same problem. When I replaced the shift cable it allowed the switch to function properly.

 

[Wave34]

Also, the high pressure pump has a check valve that may be stuck, and inside the cell there is some type of low pressure check valve that could stick too, along with the float needle not seating correctly.

Hi,
it is possible that the check valve is stuck because my fuel rail pressure drops quite fast once the engine is turned OFF.
But, when I turn the ignition ON, the pressure goes back to 55psi.
But my fear is that there is air trapped in the line and the injectors need to inject that air before the fuel gets injected.

What is the float needle in the fuel cell. Is it like in a carburator?
It acts on the fuel feed line from the fuel tank?

I wanted to try to fix this problem without buying a scan tool. Because problems like that cannot be seen by the scan tool anyway.

 

[Wave34]

Another option would be to check your neutral safety switch in your throttle mech... I had a stiff shift cable that wouldn’t quite allow the switch to seat properly causing the same problem. When I replaced the shift cable it allowed the switch to function properly.

I think the neutral switch is OK, because, after the long first start, if I immediately turn OFF the engine and restart without touching anything, it will start right away.

 

[alldodge]

it is possible that the check valve is stuck because my fuel rail pressure drops quite fast once the engine is turned OFF.

Sounds like there is a leak, it should not drop fast. Should take at least a couple minutes to drop to zero

The tank has no pressure in it, so the leak may be the connection from HP pump to fuel line inside the tank, regulator or pump is allowing fuel to leak back thru it self

 

[Wave34]

Ok, some updates.

I looked at some videos talking about the float/needle in the fuel cell and how to test it.
I tested it, and my conclusion is it is working. When the fuel cell is full, after having the pump working, I cannot suck anything from the hose on the top because the needle closes the port.
If I disconnect the low pressure pump and run the engine only on the high pressure pump to partially empty the fuel cell, then I do the same test, it is possible to suck a lot of air before I can feel a resistance.
So that means that the float is moving from close to open.
So that's not the problem...

I also tried to ruled out one of my suspicion about carbon deposit on the back of the intake valve.
I disconnected the fuel hoses, removed the fuse of the fuel pump, and ran the engine on the injector-valve cleaner.
The day after, I still had a long cranking start, a bit less though, but not like it should be.
So, it's not that.

This morning, I went and started the engine. It started the first time!!!
The only difference with the previous days, is that the ambiant temperature is colder.
It is the same thing as 2018 and 2019, at the end of the season, when the temperature is colder, it starts right away.
I don't know if that affects the MAP sensor?
I already tested the ECT above the thermostat, and also tried to start the engine with it disconnected without any improvement.

So, the problem seems to follow the outside temperature.
Very strange.

 

[alldodge]

Looking back thru the thread no one ever asked what your motor serial number is.
Can you provide?

 

[Wave34]

Looking back thru the thread no one ever asked what your motor serial number is.
Can you provide?

It is 4012101374
2004 5.7Gi-D

 

[alldodge]

Your motor has a MAP/T (also called TMAP) which reads pressure and air temp 3858987

Being the problem appears to be temp related, this may be the issue. Concern is only info I'm finding with my limited manual is its designed to let be a code for sensor voltage low or high. In the gxi manual it list the ECT and MAT resistance should be the same, but have not found same in the Gi manual

 

[harveje]

alldodge, should the resistance be the same all the time or just after a cold soak when both sensors should be at or close to the same temp.


Wave34- have you tried to remove the vapor vent line from the manifold to see if it started any easier?
Reason- my float and needle checks good with a vacuum gauge but after engine shut down I was getting fuel and vapor pushed up the vent tube into the manifold which was enough to cause me issues... I've still not found the total issue but still collecting info.. IF you think your injector (s) are leaking you can pull the plugs and see if there wet

 

[alldodge]

Unable to say for sure as stated above, the GXI mentions the same values, the GI does not

 

[harveje]

roger that.... I'll do some digging I'm like you not much info on the GI but I've got some on the gxi somewhere.

 

[Wave34]

Wave34- have you tried to remove the vapor vent line from the manifold to see if it started any easier?
Reason- my float and needle checks good with a vacuum gauge but after engine shut down I was getting fuel and vapor pushed up the vent tube into the manifold which was enough to cause me issues... I've still not found the total issue but still collecting info.. IF you think your injector (s) are leaking you can pull the plugs and see if there wet

Yes I tried. I did like in a video I saw.
I unplugged the hose from the manifold and put that end into a clear jar, and started the engine.
The engine started right away since it was not the first start I was doing, but my test was to see if there was not any gas going into the jar, and there was not.

The place the hose connects to the manifold puzzles me.
Instead of being a normal barb fitting, it is a disc.
Like if there is a membrane inside, but there isn't. I blew and sucked on it with a hose and air was circulating both ways.
Strange, why going to the trouble to make that kind of connection when a regular fitting could have done the job?
Is it a restrictor?

 

[alldodge]

Its called a nipple, but its should be a check valve 3860290, this way if there is a backfire it doesn't go back toward the pump

 

[harveje]

Correct some call it an impulse limiter, and I think it's used to pull a small vac on the fuel cell to remove any vapor space...

 

[RobRoller]

Did you say you ever checked your Throttle position sensor? On the fords it is usually close to 1.1volts in idle or throttle closed position and goes all the way to 5volts fully open. Perhaps if your boat has one the sensor is occasionally faulty. Only way to test would be to put leads on on it with egine off and test voltage. Try to start engine. If engine starts make note of voltage. If engine does not start note voltage and increase throttle and attempt restart. If it starts note voltage. Turn engine off put throttle back to idle and attempt restart and make note of voltage if it starts or doesnt. etc..