Adding a fuel oil guage to 1994 GTS

[Grumpygeorge]

I'm thinking about adding a fuel/oil guage to my 94 Gts. Seems like it should be a relatively easy upgrade as a kit was available when it was new. I'm going to track down the guage, baffle, oil sender, harnesses and box connections and see what I can come up with. The kits found on eBay only include the guage itself, so I'll be hunting for more than just that. I'll post photos as I go keep you up on the progress. I only have $1500 in both the gts and the 96 gti behind it, including the trailer. This should be a pretty straight up project, and I won't have to lift the seat every couple hours to see where we stand on fuel.

 

[Grumpygeorge]

First Installment

I've gotten underway with the project, so here is the first installment:

No upgrade/repair/rebuild is ever as easy as it looks like it is going to be, and this one is no exception. I have already run into a couple of hurdles that I will share as I get to them.

Everything I need for the project is available on eBay, OEM Sea Doo items, and as I have found in the past, its best to go with auctions that allow you to make an offer. The following are all of the parts that should be required to complete the upgrade:

Fuel/Oil gauge P/N 278000496 from a 1997 SPX
Oil Sending unit P/N 278000417 from a 1994 XP
Fuel Baffle P/N 275500023 122 226All apparently the same
Wiring Harness P/N 278000402 New old stock

The Fuel/Oil gauge was listed at $75, and is in very good condition. I offered $40, the seller countered $45 and about $7 shipping, so i was happy with that. The oil sending unit for the oil tank was used as well, listed at $10 with free shipping, so that was a deal on its own. I am basically upgrading to the GSX model minus the speedo, so i am using the GTX parts list as the resource. I haven't received the baffle or harness yet.


Since the original fuel lines were still in place, there is no time like the present to correct that problem while I am taking half the PWC apart. I ordered fuel line from JEGS.com at 25ft for 15.99 plus tax and shipping, which put it at $1 a foot. Looks like I will also need a fuel selector switch since the old one is filled with gum from the old lines (see pics). The fuel filter/water trap is clean and gum free, so it will get a new screen and go back into service.

Starting the project:
I removed the fuel tank straps and oil tank straps, hoping to remove the tank without removing the oil tank right away. After draining the tank with a siphon pump, I was able to lift it enough to slide it forward and out from under the oil tank, which I supported with an oil bottle for the time being. In order to replace all of the lines in the proper positions, I used colored zip ties at each end of the fuel lines, each line being designated by a particular color. (see pics) Then I cut the lines just before their termination point, leaving the colored zip ties on the clamps for now.
(I was able to release the original clamps using a small straight blade screw driver, so I will be reusing them as I can)

Once the lines were no longer keeping the tank in place, I removed it through the front storage hatch. The storage bin and hose vent were easily removed before starting.
All fuel remaining was removed, and the tank was cleaned out with warm water and dawn dish washing liquid, thoroughly rinsed, and set up to dry, top opening facing down and a fan blowing in the side fill opening.

Next I removed the entire fuel filter/water trap assembly, taking care to keep my zip ties in place, followed by removing the fuel selector valve with zip ties in place.

At this point I moved aft to see what needed removed to get the oil tank out. Up until this point, I had no idea how the oil injection system worked, so I headed in the computer to see what I could find out. If you don’t already know, the oil tank provides oil for injection into the fuel/air mixture to lubricate the piston rings/cylinders, as well as providing an oil bath in the lower end of the crankcase. I am still wrapping my head around this. There is a larger oil line from the bottom of the oil tank going to the lower crankcase on the carb side, and a large oil line returning to the top of the oil tank from the lower crankcase on the exhaust side, which is acting as a level against the oil in the tank, if that makes sense. There is a smaller line running to a filter and then into the oil pump. Two very small lines exit the pump through banjo fittings and enter the rotary valve chamber. On my particular pump, one of those lines is broken off and lying in the bottom of the hull. (see pics)

Oddly enough, I had checked the compression in the cylinders only a couple hours before this discovery and they are both even at 150psi. Wonders never cease. Since the oil tank is coming out and the carbs are getting rebuilt, may as well rebuild the oil pump and install all new tygon plumbing there as well. Like I said at the beginning of this post, its never as easy as it looks like its going to be.

I removed the air box, flame arrestor and carb keeping all of my zip ties in place.


In the next few days, time allowing, I will remove the oil from the tank and crankcase, remove the oil pump and oil filter, and order a rebuild kit for the pump and the carburetor.

Going forward, my shopping list looks like this:

1. Hand suction pump from HF to drain the oil tank and crankcase
2. Oil lines in the various sizes needed
3. Fuel filter
4. Oil filter
5. Fuel selector valve
6. Clamps
7. Spark plugs x 4
8. Carb and oil pump rebuild kits

Task list as I see it:

1.Drain oil tank and remove it
2. Remove oil pump, rebuild it, install it
3. Rebuild carburetor and install it
4.Open electrical box and drill for new harness
5. Hole saw oil tank for sending unit, clean it out, install new lines and sending unit
6. Hole saw dash to accept new gauge and install gauge
7. Install baffle in tank, attach fuel lines, fuel filter, and fuel selector
8. Connect wiring harness to electrical box and seal it
9. Install fuel and oil tanks, install all appropriate lines, filters and valves and connect to wiring harness
10. Bleed and flow oil in pump before starting engine
11. Adjust carb as much as possible before starting
12. Connect water and hose pincher, run and tune carb
13. Drop it in the river and make final carb adjustments.

I’ll keep you updated,

Grumpy George

 

[Grumpygeorge]

I've made a few interesting discoveries on my quest to add a fuel gauge to this GTS. First, there are a multitude of available parts on eBay to do the job. I was able to secure pretty much every part necessary in a couple of hours, and the prices have been pretty reasonable.
Second, similar parts from 1996-97 that should work, won't necessarily. Here's why:
The fuel baffle from 1994 used the same technology to determine the amount of fuel in the tank as a 1997, but the resistors on the sending unit are reversed, so your baffle and gauge need to be from the same era. That goes for the oil pick up as well.

In my case, I have decided not to buy a new baffle, but to instead try to fabricate a new printed circuit board and adapt it to my baffle, with the resistors assembled to work with the 1997 gauge I purchased, and adding a new float. The baffle is exactly the same as a sending unit baffle minus the electrical gear inside and the wires and plug. The resistance values for the board are found in the shop manual for the year of the gauge I am using. According to the wiring diagrams, the MPEM supplies the power to the gauges, but that is it. So any gauge/sending unit should work with any MPEM that has an open "hot" (red) lead. I would not recommend using any but OEM SeaDoo wiring harnesses.

I tested the 1997 SPX gauge using a 9v battery to power it (purple is positive, black is negative), and shorted the leads for the fuel (pink leads) and the leads for the oil (blue leads) directly, and that told me that 0 ohms resistance is "Full" on the fuel side, and that 0 ohms resistance on the oil side is "Full" (or not low, as the oil light only indicates when the oil is low or empty).

So, in the next few days, the supplies I need to fabricate the pc board for the baffle should arrive and production can begin. In the mean time, I have removed the fuel and oil tanks, and begun replacing every inch of fuel line, fuel selector and fuel filter, as well as ordered a rebuild kit for the carb.

Powered up, fuel and oil circuits shorted, oil light off, fuel gauge reading full

Powered and oil circuit shorted, fuel reads empty, oil light off

Powered up, fuel circuit shorted, oil circuit open, fuel reads full, low oil warning light on.