95 Ski Nautique, fuel injection prob...

[gitnmybelly]

i have a 95 ski nautique w/ 351 ford, the injectors do not seem to be squirting fuel. i have fuel pressure, and fuel is getting to the injectors. but i dont seem to be getting any signal to the injectors to fire it up. could someone please help me diagnose this prob. breakers seem like they havent been popped. need some direction... thanx in advance

not floatin my boat!

alG

[nms1991]

RE: 95 Ski Nautique, fuel injection prob...

Which engine? Gt-40 or TBI?

[gitnmybelly]

TBI...

its the TBI

[DavidF]

RE: TBI...

I have the same engine. I suppose you have checked the fuel pressure at the schraeder (sp?) valve to determine you indeed have fuel pressure and both the high and low pressure pumps are running. All three of the circuit breakers are closed. Unplug and clean the contacts on the interupter (distributor). If the ECU does not get a good signal from the interupter (to locate crank position) then the engine will NOT start (i.e. the injectors will not spray fuel). There is another relay located next to the fuel pump relay, but for the life of me, I am drawing a blank on what it does. Make sure you check the functionality of this relay. Also look for a broken or burned wire/connection (long shot).

Let me/us know what you find. My PCM TBI book is at home, but if I remember, I will bring it to work tomorrow and will be able to help you trouble shoot a little better (i.e. exact sequence of operation that allows the engine to start).

[KTompkins]

RE: TBI...

So I gather that you ruled out an ignition problem. You are getting it to fire but its not running smoothly.

[DavidF]

RE: TBI...

The original post states that the injectors are not operating, thus not delivering fuel. This indicates a problem with an input signal to the computer. For instance, if the computer cannot determine crankshaft position, then it will not allow the injectors to operate and the engine will not start.

It could also be the main relay, which I would check first and foremost.

[gitnmybelly]

RE: TBI...

im getting fire. put fuel in the butterflies and it cranked right up. i have fuel pressure 16-18lbs. so i have ruled out fire, and fuel pump. i am stuck with the injectors not getting signal or power. put a test light on the injector plug and got no power to them. (ACC not cranking. i was told that they should recieve power and when grounded it allow them to squirt fuel) so its either a relay, which i dont know where the main relay is. or the breaker. but it does not seem to be tripped unless its burnt out. thanx guys for helping me on this quest to get back on the lake.

[DavidF]

RE: TBI...

The relay is located on the port side of the engine and is mounted to the plate that carries the FI computer module which is just aft of the coil packs. There are two relays side by side, one is the fuel pump relay. If I remember, I will bring my manual to work tomorrow and then I can let you know what wires carries critical signals to allow the injectors to operate.

Incidentally, I found my fuel pressure to be between 16-18 psi (specs call for 15), but Mark at PCM recommended 13psi. I lowered mine to help with richness at idle. Since I rarely (more like never) operate at WOT, I am not worried about being lean at WOT.

As a last resort, after nothing else works, you can send the ECU to me and I can plug it into my engine to see if works properly. Otherwise, you are looking at an expensive replacement part.

[gitnmybelly]

relay good

...connections cleaned. still no fuel.

[DavidF]

RE: relay good

Take it step by step...
1) Do you have 12v at terminal "P" of the EFI module with the key in the run position?
2) When you first turn on the key, the IAC motor pintle should fully retract. Is it doing this? Remove the IAC to watch if it retracts with key in run position. If it is already retracted, does it vibrate/jiggle and little in an attempt to reset/retract? If yes, then you are getting 12v to the EFI module.
3) You should hear the fuel pumps running when you first turn the key to run. The pumps should run for no longer than about 5 secs...probably less. If they do not, check the pump relay(s).
4) You should have regulated 5v (from teminal "N" of the EFI module) to terminal "C" at the TPS, BARO, and MAP sensors. Check this with the key in the run position. These sensor send a return signal back to the EFI module via teminal "B" at each sensor (orange, grey/white, light green respectively).
5) You should have regulated 5v from terminal "J" of the EFI module via a dark blue wire to the intake air temperature sensor. No return signal
6) You should have regulated 5v from terminal "K" of the EFI module via a brown wire to the coolant temperature sensor. No return signal.
7) The EFI module and the Pro-Tec module communicate with each other via the green/purple wire connected to terminal "C" of each module. No signal from the Pro-Tec module, then the injectors will NOT operate (check continuity of this wire).
8) Terminal "M" of both modules are connected to ground along with black wires from sensors.
9) Power for the injector circuit (and fuel pump) is taken from the 15amp breaker via the 60 amp breaker.
10) You should have 12v to terminal 30 of the EFI module relay at all times (key on or off). A faulty relay here could be your problem. However, with a faulty EFI module relay, your fuel pump should not operate at all. See above.
11) The injector power circuit is completed via terminal #87 of the fuel pump plug via a red wire which connects to terminal "D" of the injector plug.
12) The injectors only get a "firing" signal when the engine speed reaches 300 rpms or higher. The firing control is completed through grounding control within the EFI module. This means that if you ground the input signal, the injector should fire as it normally has power at all times.

So, what does some of this mean? If the EFI module and/or the Pro-Tec module cannot read engine speed, then it will not "fire" the injectors. The engine speed is determined via the interrupter (distributor). The interrupter is a magnetic device not likely to fail....but anything is possible. Since you claim that the engine is getting spark (ie. it runs when fuel poured down throttle body) then I tend to think the interrupter is working...otherwise, you would not have spark. So, trace the circuits as I have laid them out (check voltage and continuity) and look for the broken chain. May want to replace that EFI module relay first and foremost and check the wiring at same.

Good luck.

[gitnmybelly]

RE: relay good

thanx for the help. im gonna trouble shoot it this weekend when i have more time. thanx again and i will keep you posted.

[darylforman]

These posts are old but I wanted to provide some additional info. I was having the exact same problem as "gitnmybelly" with my 1994 Ski Nautique. I followed DavidF trouble shooting steps and I figured out what was going on. It was the interrupter (distributor). It was not giving the RPM information to the computer. The work around is to turn the key to the on position and wait for the fuel pump to shut off. Then turn the key off and back on, then start the engine within the first 5 seconds while the Injectors and fuel pump still have power. After that the injectors and fuel pump will never get power because the computer doesn't know your trying to start it (min. of 300 RPM). Once it's started you are good. I am not sure why but I think the computer can detect that the engine is running and turns the fuel pump and injectors back on (FYI - on my boat this is done by providing a ground to the fuel pump/injector relay).

I just purchased a DUI distributor as a replacement. I am going to see if I can keep the TBI and run it with the DUI distributor. If I can't make that work, it may get a carb!

Daryl

[Jonny Quest]

Your 1994 has throttle body EFI and also has ProTec engine management system, correct? There are 4 rectangular black coil packs in the rear of the engine over the bell housing. The sparkplug wires run back to the 4 coil packs, correct? If so, have you considered installing your DUI and retro-convert to carburetor? Running your EFI on ProTec without the trigger may be difficult. With a good carb and a DUI dizzy, you will get very close to your TBI in terms of performance...with much less hassle factor.

[rytug208]

Any updates on getting the tbi to still work? Darylforman. I have a 95 nautique with the TBI and it’s running but cuts out over 2500 rpm, wanting to find a fix without going to a carb and dist. Anyone ever looked into Holley sniper 2 throttle body as a solution?

[NautiqueJeff]

rytug208 I am going to guess that your check engine light is on too. If so, you're likely in limp mode caused by the SLOW system.

Only two things can cause the boat to go into limp mode. One is an overheat condition being sensed, and one is a low oil pressure condition being sensed. If you really are experiencing either of those conditions, you need to figure out why. Sometimes the switches that control the limp mode fail though, and activate limp mode even though there is no real issue. This would cause your gauges to read normal readings, but the switches for the SLOW system are signaling a problem, even though there is none. These switches are SEPARATE from the sensors for the gauges.

My bet is that the oil pressure switch has failed. You can disconnect the wire from that switch, and that should allow you to run the boat normally until you can get a new switch. It may also be the water temperature switch, and same deal with that, just disconnect the wire until you can get a new one and the boat will run fine.

Here's the oil pressure switch:
https://www.nautiqueparts.com/produc...nd-gm-to-2006/

Here's the water temperature switch:
https://www.nautiqueparts.com/produc...-mpi-r020014a/

We're talking about the SLOW system here. See diagram below.

These are the ONLY things that can trigger limp mode. Nothing else can do it.