View Full Version : Wonbt Start 350 Indmar TBI Engine

05-03-2006, 06:15 PM
"1994 Mastercraft 190 Prostar Indmar 350 V8 TBI

No fuel prime when trying to start after skiing sometime 2-3% of the time?

New fuel pump last year, new fuel filters, runs great 98% of the time start right away the first time.

any help thanks"

05-03-2006, 06:53 PM
"You may be able to find the answer at www.tmcowners.com (""). If you do a search, it's bound to be there.

Look at the back of the motor where the ground wires are attached to the block. Do a wiggle test and see if anything is loose. Maybe, cleaning the ground point will take care of this. Also, make sure the battery terminals are very clean.

Otherwise, what have you checked so far? Are the gauges coming to life? If not, check the safety switch. I would also look at the fuel pump relay and the fuses.

If you have a multi-meter, set it to AC voltage and probe the purple/white wire at the distributor or the ECM. If you see 1-2Vac while cranking, check the two wire connector on the fuel pump. The ECM needs to see 300 RPM or more to trigger the relay during cranking.

Your fuel pump relay needs to have 12Vdc on pin 30, where there is a pink wire. There's a green/white wire from the ECM on pin 85, which triggers the relay. Pin 86 goes to ground and is black, while pin 87 has a grey wire going to the pump.

If you don't see 12Vdc on pin 30 (pink wire) at all, look at the fuel pump relay fuse and if that's good (test it, don't just look at it), check for voltage at the MEFI system relay."

05-04-2006, 11:25 AM
"I have checked most of that.

When it won't start and I see no fuel priming the carb, just spray starting fluid into carb and it starts and runs fine then, just needs fuel to fire.

When it start normally you see pulsing fuel coming into carb.

The next time (1-2% of the time) none and no start?

Thanks for your help"

05-04-2006, 02:39 PM
"Checking most of it won't tell you where the problem is, unfortunately. You already ruled out spark so now it's an electrical issue. Again, the Mastercraft site I provided a link for is a really good place to look for info like this. If you ski a lot, you'll probably make some friends, too. Very helpful bunch. I was a MasterCraft tech for about 5 years and was a moderator on that site for over two years so this is very familiar territory for me.

Print a copy of my last post if you don't have a manual and check pins 30, 85 and 86, specifically. If you don't hear a click when the pump is supposed to prime, these will lead you in the direction of the problem. If you put 12V on pin 85, it should prime if pin 30 has 12V on it and 86 has a good ground connection . If you don't get a click and have voltage on pins 30 and 85, swap the relay with one of the others. They're all the same and can be used for diagnosis. If you have voltage on pin 87 and at the pump connector, check the pump's ground by turning the key on, grounding the pump's ground terminal and turning the key to ON. If it primes, it's probably the pump's ground connection.

The first thing I would do is clean all of the motor's grounds. If the problem goes away, you can be pretty sure that was the cause.

I have a TBI in my truck, too."

05-16-2006, 05:56 PM
"Hi Jim,
Still working on this. Have heard there was a problem with the 1994 TBI Indmar engines doing this but the one solve was to flash or replace the ecm.

As to your question, 12v, even when the TBI doesn't pulse fuel on starting the fuel pump primes every time you turn the key off and on but no fuel on going to start mode. So I believe the fuel pump is not the problem and is brand new.

It could be a heat question, but then I can turn the engine off right away after spraying starting fluid in and starting because of non fuel pulse and next time will start normal.

I tried starting and stopping it 6 times in a row and it didn't happen.

I set the timing at 8 but I don't think that would be the problem. Something just sometime does not say pulse fuel for start?

Thanks again also my skiers thank you for your help."

05-17-2006, 02:06 AM
"Timing is supposed to be at 10 BTDC but you need to put it in diagnostic mode to defeat spark stabilization and get it up to 1000 RPM to set base timing. You can use a scan tool or a paperclip for this. Bend a paperclip into a V and insert the tips into the A and B positions on the DTC connector. Turn the key to ON and watch the dash light flash 1..2..(this is actually 12) three times. If it just flashes 12 again (three times), you don't have any stored codes. If it shows any other codes in between, post them here. Start the motor, get it to 1000RPM and set your timing to 10 degrees BTDC. Pull the paperclip out and your timing will be correct.

Try to get the relay to latch manually and see if it's intermittent. If it does prove to be intermittent, swap that relay with another one.

If I understand you, it primes but doesn't always pump during crank. If so, check the purple/white wire from the distributor for 1-2 Vdc during crank. If you don't see this, you may have a bad ground on the IC module (in the distributor) or the IC module may actually be bad. The ECM absolutely needs to see this signal to fire the fuel pump relay at that time."

05-17-2006, 11:45 AM
"Thanks Jim,

I will go back and set my timing the right way and try and check the purple/white wire when it doesn't prime on start. As you can see I'm trying to be a mechanic but no manual to do it right. If it is the IC module could I fix it? And to get it right the first time where is the DTC points I put the V paper clip in?

Soon hopefully I will be able to ski boat problem free. Another person with the same boat said he had to change to a 96 ECM?

Thanks again I owe you a ski ride if your out west."

05-17-2006, 12:07 PM
"The IC module is in the distributor. Remove the cap and it's the plate with the two ports on it for the harnesses. It's available at any auto parts store or GM dealer.

Also, don't use starting fluid- get an empty mustard bottle and squirt some gas into the throttle body. The bottle won't usually leak when the tip is closed (assuming it's very clean) and the gas is less explosive.

Make sure the distributor is well grounded. Loosen the hold-down and clean the metal it mates with, then put some grease on the clean surface.

The DTC port in at the rear of the motor (usually the driver's side) and to make it easier to get to, release the gas shocks for the motor box cover and lay it back onto the floor or maybe a PFD. Slide the plastic cover off and look for the A and B terminals. It's the same port as in a GM car or truck.

Where are you located? If you're in PHX, Mastercraft of AZ is a good dealer and if you just don't like the MC dealer near you (in Southern CA, I can understand this- my cousin has had a bad time with that one) you can go to any Indmar servicer for parts and advice. Again, go to www.tmcowners.com ("") for more links to threads that may apply to your boat. Someone on that forum is bound to be near you and you may even know some of them already.

While it's possible for the ECM to go bad, it's unusual. He needed to go to the '96 version because there aren't any '94-'95 units available. You can't, however, go easily to anything newer because they changed the relay trigger outputs to negative and went to an internal knock sensor module, so the harness would have to be modified. Still possible, though.

If you have a multi-meter, check the green/white wire going to the fuel pump relay for voltage while cranking and for two seconds when you turn the key to ON. Another thing I just thought of is the pickup coil in the distributor, which may be going bad."

05-18-2006, 11:38 AM
"Thanks Jim,

I now have the timing at 10 and it start better. Checked ground on distributor. Could not get V reading on purple/white wire but must be the way I was doing it because it still started every time.

Found the IC module and seeing how much to replace today before skiing tonight. Will let you know how starting goes while we ski after work.

I will use gas from now on. The boat had been neglected for years before I bought it, just sat out side with no coverings, so moisture could be a problem even tho low hours for 12 year old boat just turned 496hrs."

05-18-2006, 11:56 AM
"Not that the IC module can't be the problem but now that I know it sat for a long time without being covered, go through and check all of the butt splices under the dash, particularily anything on the purple lead, any of the terminals on the ignition switch, all of the grounds on the motor and the solenoid(s) before changing anything. Loosen the hold-down screws on the IC module and see if the mating surfaces are clean. Since there was undoubtedly condensation on everything, any contact could be the culprit. The fuel pump's relay ground is at the back of the motor and I have seen corrosion cause the problem you're having. Remove the battery cables and take the ECM plugs off, then re-insert them to make new contact. List what you do so you don't repeat anything but be thorough."

06-12-2006, 11:44 PM
"What happened with your boat- is there any improvement?

Where are you "out west"? You didn't buy it from someone in Canyon Lake, did you?"

06-01-2008, 01:42 PM
"Could someone tell me where the damn fuel pump relay and fuse are? It may sound like a stupid question, but I'm hooped.
Sorry!!!! 1998 Moomba Mobius Indmar 350."