99 SN GT40 Fuel Supply

At the end of last seaon, after a couple passes through the course, my engine died when I applied power to take off. It would idle fine, but would die with a gasping sound every time I gave it gas. Couldn't even power up on the trailer.

Since that time, I booght a pressure gauge and have observed some very strange readings. It will run about 35 psi, then fluctuate widly and go to zero. I removed the Regulator hose and saw it momentarily jump to 40 psi, then go through all the ups and downs as before.

The pumps do not always prime, so I have been inclined to think it is a power issue to the pumps. I replaced the relays, as I had sufferred through that diagnosis two years ago, and have a two year old low pressure pump, ant-syphon valve, and kill switch to thank for that one.

The plugs and distributor cap and rotor are new.

The hi pressure pump and filter are new along with the FCC housing, as I developed a gas leak through the fitting on top of the old FCC when I was checking the hi pressure pump and filter. (that was a $450 ouch). I also replaced the 15 amp circuit breaker, as that seemed like it was frozen.

I completely drained the fuel tank when I repacked the rudder this spring, so I am pretty sure nothing in the tank is plugging the line. I have no in line filter, only the one in the fcc.

I have followed the electrical lines back to the fuses, and all connections seem clean and tight.

I want to jump the low pressure pump direct to the battery, and am making up some alligator clips to go direct to the low pressure pump to see if this makes a difference.

Does anyone know what terminal on the low pressure pump is positive vs negative? I am thinking I need to run off the battery to the positive post and vice versa for negative. I am thinking this might confirm that the low pressure pump is good.

The other question is what else can I look at that would cutoff power to the pumps? I replaced the relay this year, as I have two spare ones. That made the pumps prime, and I thought I might have fixed it like last time, but, that was just a coincidence of the problem.

What is odd is that the engine will not take gas, consistently. If the pumps are randomly running, you would think that I could at least get rpms randomly.

This one is a real head scratcher. The guys from Ski Dim and White Lake have been great, but we are just shooting at the sky right now, and the season is right around the corner. My dealer is no longer in business, and the next guy is 2 hours away, and I don't know him well.

Any ideas?

8122, I am somewhat electrically challenged. I have a meter, but really don't know how to use it very well.

How would I check for ground?

I have turned a few wrenches in my time, but not dealt with a lot of electrical stuff. My dad was the electrician, plumber, welder, etc....

Thanks

Al,
Set the meter to any Ohm range. What happens when you touch the two probes?

If one of the probes was grounded on the block and then you touched the ground wire feeding the pump with the other probe, what should happen?

What have you been using the meter for?

Al you can make both pumps run by shorting the end terminal of the STO connector to ground (ECC Test connector above relays). You should have 39 +- 3psi with key on engine off and 31 +- 3psi at idle. With the vacuum hose removed at regulator and engine running you should see max pressure mine reads almost 44psi.

I would also check the volume of fuel the low pressure pump puts out.

I am just south of Toledo. The lake is alongside the Ohio turnpike. Look at Google Ski Sites, it is The Slalom Club (I know, real creative name).

My dad gave me the meter. I guess I have tested batteries with it, and that is about the extent of me using it.....

No fuse on my battery line. I have seen that has caused intermittent problems for some, but I don't have one. Good thought though.    

Here is a link to a video I made of the boat running in the driveway. I removed the regulator hose, and this time, the pressure had dropped to zero, but you can hear the rpms pick up a little. When I did this when the pressure was at 35 lbs, it jumped to 40.

You can hear the pumps sucking air as the pressure drops.

The boat ran great and then viola, this is what it did on the lake on the last ski ride for last season.

http://www.youtube.com/watch?v=0hihpHcuNvY

Ignore the last paragraph. I was going to delete it after I changed the paragraph above it. :-)

There are a number of us GT-40 folks lurking on the forums (a number of them have quite a bit of experience with troubleshooting the ECC, etc.). So I'd say you are in good hands (keeping in mind how much you are paying for this advice....)   

Sorry, I just now saw the video.

First, what is that hissing noise we hear when the pressure gauge is climbing back up to normal pressure? Where is that coming from?

Second, something is weird with your pressure gauge, how it is hooked up, or something. If the pressure in the rails drops to zero, the engine dies. It will not run if there is no pressure at the rails (the injectors open, but there is no pressure to push the gas into the manifold).

So something is weird since it is still running (albeit loping) with no pressure indicated, but it will be helpful to understand where that hissing is coming from. Note: It sounds similar to the loping issue that a number of us are dealing with (with some, there is cold start loping, and with others, it is hot restart loping). However, with my loping, the PSI stays between 32 and 40. So I don't think it is related (a number of us are working through this), but the loping idle in your video is very similar.

Anyway, make sure your gauge is on securely (tight), let us know what that hissing noise is when the pressure is moving back up. Then use the jump that Mark showed you; that will keep the pumps on with the ignition on (instead of them turning off after one second). You can then test each one (low pressure by the sound of fuel returning), and high pressure by your pressure gauge.

Oh, and you said it sounded like the pumps were sucking air. I don't know if you could hear that with the pumps on and the engine off, but I'm pretty sure there is no way you would be able to hear anything like that if the engine is running. I'll watch/listen to the video a few more times in the next day or so to see if I can pick up anything.

Like slmskrs(Gordon) mentioned not sure what sort of connection you have on your pressure gauge but zero pressure and engine still running is weird. I assume it is connected to Schrader valve on fuel rail. I remove the valve inside of this connection before I hook my gauge up as the connection does not depress the valve properly.

I assume the hissing noise is there when you open the throttle? With the pumps jumped to run you should hear the pumps run without the engine and see if that noise is still there.

It sounds like a vacuum leak but it might be that the mixture is way to lean. When you removed the vacuum hose to pressure regulator it should have leaned the mixture out and increased idle speed if there was enough fuel available. So it seems like it is starving for fuel. But then you mention black smoke and smell of running rich.

Could it be a poor spark problem?

The TFI module is a known problem area on these engines check connections to TFI module and pull a plug and check for nice fat spark.

Confirm connection and correct reading of pressure gauge and get back to us.

It is a nice demonstration of the engine idle loping that Gordon is chasing. I have had that a few times myself. Sounds like a engine with a big camshaft and lots of overlap.

By the way nice colour scheme and don't let the wife know that the hot water out of the exhaust is what killed the grass.

Al, no fuel should come out of the Schrader connection with the valve removed and the gauge in place. Leave the adapter on the end of the gauge as it is. This rules out any problem with the gauge fitting opening the valve. This is for testing purposes only. Would not leave it for any length of time that way.

Need to confirm those pressure readings first both at idle and with the jumper on STO connector.

Also check the output of low pressure pump as mentioned previously. This is achieved by disconnecting the high pressure pump electrical connections at FCC. Remove fuel hose from low pressure pump to FCC and place it in a container. Install the jumper to STO terminal it should pump about a US Quart in around 15-20 seconds. I have a Schrader valve on top of my FCC not sure if the new FCC you fitted still has one. The reading should be the same on the fuel rail anyway.

If you have a electrical problem as you suspect the grounded jumper on STO connector should help you troubleshoot. You will hear the pumps running I would wiggle all the connections on both the fuel pump and EEC relays plus tap the connections on all 3 cct breakers located on computer bracket. If the pumps stop you will know which connection to investigate further. If you have not already downloaded the GT40 manual from the reference section do so and printout page 281 and 282. It gives you the wiring diagram for the fuel pump operation.

M3Fan wrote: If my GT40 starts loping this summer, I'm blaming you guys for talking about it so much and jinxing it. Seriously though, as these powerplants start getting past 15 years old it's going to be interesting to see how often we start talking about them! I've seen more GT40 threads over the past few months than I have since the site launched.

Well, I'm not going to mention that I joined in January.......       Actually, other than the loping issue (which I've had for probably a decade) and the water jacket cracks in the heads (typical of a GT40), I have had to replace my low pressure pump and clean out a small screen mesh in the top hose connection at the fuel tank......in almost 1,400 hours. It has been incredibly reliable, including the electronics. Head cracks are irritating as it is a known problem, but other than that, I think it is an extremely reliable powerplant (much better than my old carb'ed PCM 351 in my old boat).

AMB: A couple of additional questions while we're waiting for the results of your next set of tests.

Is there any difference between cold running and warm running? In other words, does this happen when you first start it (with a hose), or does it need to warm up before it starts doing it?

How long after you start it does it start having the problem? I saw in the video how when the pressure is at the correct PSI range, the engine runs correctly.

So I'm interested in the timing of when it starts.   For example, if it is doing it and you shut it off and then restart, does it continue, or does it run fine for a little bit before it does it again?

If it does it fairly soon after you start, it will be interesting to see if you hear the pump noise and see the pressure drop about the same time when you jump the pumps.

Also, as Mark said, it is a good idea to remove the shrader valve to hook up the gauge as I experienced the same problem (not properly depressing the valve). Make sure you have no pressure before you do it. I managed to get it tight enough to work, but you do not want to shear the valve off.

Let us know on the above, and also the results when you jump the pumps (do you hear gas splashing back into the tank, does the sound happen (and pressure drop) when only the pumps are running, if you hear splashing, what is the flow of the low pressure pump (filling a container), etc.

Speaking of starving, a problem I had previously which had different symptoms is that there is a small screen mesh in the top of the tank where the inlet hose connects. That had actually gotten plugged with dirt, etc., and it finally got so bad that while it would idle, we couldn't cruise for very long, and finally couldn't even drive through the course without it cutting out. Long story short, it ended up being that little screen--pulled it out, cleaned it up, put it back in, and everything was good. I do not recall hearing the type of "starvation" sounds that you have, the engine just stuttered and slowed. Not to say that it didn't make the starvation noise, but since I was at speed when it would happen, there could have been too many other noises to hear it (or I just don't remember....).

If you do get it figured out, could you weigh in here:
edited link:
http://www.correctcraftfan.com/forum/forum_posts.asp?TID=25584&title=poor-mans-gt40-diagnosis

Also, have you confirmed your fuel tank is venting properly, try opening your fuel cap and see if this helps.

Also, you may have one more fuel filter, under the removable floor section behind the motorbox. Some of them have this, some don't. If you do, it is a possible restriction if it's dirty.

AMB wrote: The thing that leads me to think it is electrical is that the pumps don't prime with ignition on. Sometimes they do, and sometimes they don't, and everything I have read is they prime every time. When my pressure dropped to zero, I shut it off and listened, and no prime.

Sorry, I glossed over the "prime" info you gave and went off looking in other directions. I'd definitely check all of the connections, grounds, etc. especially to the relay and to the ECC since the ECC controls the prime relay. Maybe you're getting intermittent power to the ECC. Also, I don't know where it is, but I'd check wherever the pumps are grounded to. Also make sure your ground connections at the key are good. Poor grounding causes a lot of problems on these (and probably any other) boats.

Ok guys, I turned the ignition on and started wiggling. I got back to the STO and just touched it and the pumps primed. I squeezed it together and turned ignition on and off a few times, primed every time and the pressure went to 40psi.

I then took apart the connector and it felt too easy, but I did break the plastic piece on the TEST Connector. I jumped with a wire lead and the pump then kept pumping and I could hear gas dumping in the tank, and pressure was 40 psi.

Trying to remain calm, as I had false positives before.. but holy crap Batman, this has been one PITA!

I do have a question though, there was a smaller gray plug at the top of the pic above, that looks like it just popped out of the STO, and it is sort of hard to see if it should snap in or just rest in there with no purpose. There is another dead end looking larger gray plug, which is a the bottom of the pic above. Do I need to do something with the smaller connector?

Also, I assume White Lake and Skidim carry the Test Connector? The black piece mounted on the plate with a plastic snap in fastener.

THANKS A MILLION GUYS!!! WEATHER IS WARMING UP AND THE BOAT HAS TO GET RUNNING!!!

AB