Help !!!!! with 1994 TBI
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=4659
Printed Date: November-27-2024 at 2:54pm
Topic: Help !!!!! with 1994 TBI
Posted By: kevman38
Subject: Help !!!!! with 1994 TBI
Date Posted: August-29-2006 at 10:50am
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Hey guy's I been a correct craft owner for 12 years never a moment's worth of trouble so I guess It's about time. I have a 1994 tbi 351 It will start and run about 3 min and then shut down like you you pulled the kill switch. Let it rest about 20 min and it will start up run about 3 min and shut down again. Fuel pressure is 13 psi (perminantly mounted a guage to monitor). Discount inboard sent me a protech ignition pack still has same problem. What is next computer ? crank sensor ? electrical short ? Should I convert back to a carb/distributer due to the limited supply of TBI parts ? Thanks for your help.
Kevin |
Replies:
Posted By: Tim D
Date Posted: August-29-2006 at 3:34pm
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Does it have an oil pressure sensor? ------------- Tim D |
Posted By: 79nautique
Date Posted: August-29-2006 at 6:13pm
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what about the fuel pump relays? read alot about guys having to replace them recently. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: David F
Date Posted: August-30-2006 at 10:29am
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I spoke with Kevin on the phone yesterday and we did some troubleshooting. It seems he is getting good fuel pressure when the problem occurs (ie. the pressure on his permanently installed gauge does not drop). Thus we concluded that the fuel pump relays and pumps are working. Plus Keven can hear them running.
The oil pressure switch and coolant temperature switch, if faulty, will not cause the engine to die or prevent it from starting. The switches merely illuminate the warning light and send the computer into limp mode. The crank position sensor is part of the interupter (distributor) and I suppose could be a heat related problem showing up within. Kevin and I did not discuss this scenario. Once the engine has a cool down period, it restarts. Finally, Kevin mentioned that if he holds the ignition switch in the starting position for a longer than normal period, the engine will act as if it wants to start (i.e fires, but does not run). This makes me think that the "ignition on" portion of the switch could be faulty. An internal poor connection with high resistance that heats up and looses electrical continuity thus the engine dies. Holding the key to the start forces a weak reconnect of the ignition circuit and it attempts run. I could be way off, but a cheap hunch to test. More than likely, it will end up being a new ECM that solves the problem. TBI related sensor failure should not cause a dead engine scenario, just a richer than normal, fail safe, fuel delivery map. So, my thoughts for possible sources are: Fuel delivery: verified to not be the problem. Ignition switch/electrical problem. ECM Interupter Good luck Kevin and let us know what you discover. <edit> Forgot that Kevin mentioned that while cranking he can see fuel being delivered. Again this means not pump related AND not interupter (crank position) related as the ECM will only fire the injectors once it knows crank position and gets a 300 rpm crank speed signal. So, if the injectors are firing, the interupter is working. AND, per another thread, disconnect the tachometer while testing. I believe it is the grey wire with a single connector close to the main harness plug going into the ECM. <edit again> Ensure the circuit breakers are not having some sort of internal problem. once the engine quits, make sure there is continuity across the breakers. ------------- |
Posted By: 79nautique
Date Posted: August-30-2006 at 10:53am
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did he replace the coil pack and not the module? should have tried the module first, if it was a coil pack it would just misfire and not take out the spark all together. When it happens verify the spark is being lost by pulling a plug or wire and looking for the spark. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: David F
Date Posted: August-30-2006 at 11:00am
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Kevin just replaced a coil pack, not the module. I told him the same thing, one dead coil pack will just cause the engine to run extremely rough, but it should run. If I remember, there are four seperate coils (replacable in pairs), so the likely hood of all four (or both modules) failing at once would be remote. I suppose on pack (ie. two coils) could fail and thus kill the spark to half the engine.
Kevin: I a$$ume you purchased one coil pack from Skidim and tried it in both positions. ------------- |
Posted By: 79nautique
Date Posted: August-30-2006 at 11:15am
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the coil pack isn't going to go out all at once it will misfire a while before it quits completely and it's extremely rare that two would go out at the same time but it is a motorola design and sucks, that's why they don't make them anymore. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: Tim D
Date Posted: August-30-2006 at 3:30pm
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If the oil pressure is low, is it set up to cut the fuel off? ------------- Tim D |
Posted By: 79nautique
Date Posted: August-30-2006 at 3:52pm
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Tim I believe it would or at least go to limp mode but it's not really getting enough time to heat up the oil to thin it out and lower the reading with it occuring in about 3 mins after start up ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: Tim D
Date Posted: August-30-2006 at 4:16pm
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I was thinking oil pump. ------------- Tim D |
Posted By: kevman38
Date Posted: August-30-2006 at 10:55pm
| You guys are fantastic !!! David you've done an excellent job explaining the troubleshooting process and relaying my problem to the rest of the forum. I am leaning towards the faulty key switch due to the fact that I have replaced the coil pack and computer to no avail. This evening, I noticed that the key switch seemed to operate intermittently in the "on" position. When the key is turned to the on position, the fuel pumps should give the engine an initial burst of fuel. However, I found while trying to start the motor several times, that the fuel pumps were not engaging. If I drag the starter, the engine starts and runs at 1200rpms, just like normal. This verifies that the crank position sensor and fuel pump/relays are opreational. So again, I am leaning towards the key switch. What do you think? Stay tuned - will bypa$$ the key switch tomorrow. Thanks again for all your help. I will post when I find out more. |
Posted By: The Dude
Date Posted: August-30-2006 at 11:40pm
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David, you called him? Wow...this is what I love about this forum. Guys really care about other guys getting their boats running. What generousity.
Kev, let us know! ------------- Mullet Free since 93 http://www.correctcraftfan.com/diaries/details.asp?ID=717&sort=&pagenum=1&yrstart=1991&yrend=1995 - 95 Sport |
Posted By: kevman38
Date Posted: September-01-2006 at 9:35am
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Hey guy's still have not had time to trouble shoot the key switch ( two in dipers + work means it's dark and I'm out of time). I have found a place that may be able to rebuild the ProTech coil pack and ECM. They repair ignition systems and ECM's for merc,omc and mercruiser. They said you have to send them your units to know for sure. The company is CDI- Rapair 256-772-3829 they are located in Madison Alabama.
Kevin |
Posted By: 79nautique
Date Posted: September-01-2006 at 10:13am
their lieing to you the coil packs can not be rebuilt they are destroyed if you try to take them apart. They are expoxy encapsulated/potted coil windings that can not be repaired only replaced, same with the modules they can only be replaced as well. The curcuit boards in the ECM can be worked on and rebuilt but it's really easier to buy one rebuilt at the parts store then paying the higher cost they might charge you. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
kevman38 wrote:Posted By: David F
Date Posted: September-01-2006 at 10:16am
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Kevin:
I think you and they will find that the units are not rebuildable. Even the ECM components and board are encapsulated in epoxy. ------------- |
Posted By: kevman38
Date Posted: September-02-2006 at 11:44am
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Hey guys as Paul Harvey say's "now for the rest of the story". Went out this morning and replaced the key switch 12 years old and 25 bucks why not rule it out. Motor started fine ran 6 min temp about 145 I said EUREKA !!! and then it shut down.Upon restart noticed the fuel pumps did not power up. I tested the low pressure side with my meter key switch in run 0 volts. let it rest about 20 min turned key switch to run re tested 12 volts. re connected started motor fuel pressure 13 psi run well for about 3 min then shut down. I'm suspecting fuel pump relay. Again if I drag the starter (keeping it energized) the motor runs 1200 rpm with the fuel pressure at 13 psi.Doe's the start position on the key switch by pa$$ the relay keeping power the fuel pumps ? I can't find my #@&*$#* shop manual.
Thanks for your help, Kevin |
Posted By: LakeBoy
Date Posted: September-02-2006 at 3:11pm
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Just thought I would jump in: See my thread "GT-40 Engine Cuts Out"
Replace the freaking relays, dude. 12.00 each from ski dim. My motor cut in and out. I'd fiddle with the relays, pulled them in and out, it worked then it didn't. Checked fuel pressure, cleaned the screens, etc, etc, etc...I got the new relays: Not one problem since. That it goes whack when it is hot tells me it is electrical related. Read the threads on this site and others. An you will see Nautiques have relay problems. Buy 5 and keep them on-board. To the rest of the forum: way to jump in and help this dude! KevMan38: If you comb this forum for other people who have had the same problem, you will come up with a list of 50 things you can check. I have done it, and I will say this: 99% of the cut out problems are electrical. Mostly connections, too. |
Posted By: The Dude
Date Posted: September-02-2006 at 4:12pm
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lb, are you being sarcastic? see 79's comment above... ------------- Mullet Free since 93 http://www.correctcraftfan.com/diaries/details.asp?ID=717&sort=&pagenum=1&yrstart=1991&yrend=1995 - 95 Sport |
Posted By: kevman38
Date Posted: September-02-2006 at 5:41pm
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well, I replaced the fuel pump relay still no power to the pumps. I've been over every connection, every ground, combed every wire with in reason looking for a bad spot or short nothing stands out.I can only find one relay. Some are saying that there are two.I still can't find my @#$#@#$$#@#$$#@#$##@# shop manual. Can you tell I'm getting frustrated !!! .When the ignition switch is in the on position I should see 12 volts to the pumps It's not there. New relay and still not there. I don't know the exact pins on the relay to meter... I suspect it would not matter as I have checked all pens to ground.... 0 volts. What am I missing, another relay ? I'm stuck. Still when the switch is held in the start pos the motor runs at 1200 rpm's @ 13 psi upon start up. This tells me cps/fuel pumps/relays are functioning ,but why not in the on /run position ? did I mention I can't find my @#$#@#$#@ manual. If ther are two fuel pump relays on a 1994 pro boss TBI motor I can only find one in the rear by the ignition coil pack. Where is number two ?
Kevin |
Posted By: 79nautique
Date Posted: September-03-2006 at 1:55am
Well If your doing this your self your going to see what you see, you cannot get from turning the key on to messuring the relays in time before the voltage is gone, replace both then try it for a run. other wise you need two, measure the relays with the meter ready to go, then have some one turn the key and whatch, don't turn the key on then go and prob and then watch.. too F' late it's not going to read anything, maybe 0, the oil pressure gauge has already sent that it's not seeing oil pressure so it shuts down. So read the voltage at the relay while someone else turns on the power and you have a reading bofore the motor is cranked over. then get a reading while it'cranking, maybe coil pack problem????? maybe relay if tested right???? ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: David F
Date Posted: September-05-2006 at 9:53am
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79 is right. The fuel pumps run a maximum of 5 secs once the key is turned on. The control module (ECM) then shuts the pumps off if no rpm signal received. (the oil pressure switch is not involved). Once the ECM gets a 300 rpm signal from the interupter (trigger) then the fuel pumps relay is pulled in.
I think there are two relays: one for both pumps and one for the ECM (again, I think but might be wrong on this...cannot remember clearly). The ECM outputs four control functions: Injectors Fuel Pump relay Idle air control ignition timing If the ECM is getting bad input from several sources, then it is probably killing one of the outputs listed above. I am still suspecting fuel pumps. However, I believe the ignition timing is also control by the knock sensor. Try disconnecting the single wire from the knock sensor (located in one of the block drains). This will still allow the engine to run, but take a potential faulty sensor out of the equation. FWIW: ECM inputs are: Manifold Absolute Pressure (MAP) Engine speed (RPM) Throttle Position (TPS) Water temp Crankshaft Position Intake air temp Barometric Pressure Battery Voltage ProTec Note the ProTec part of the above. The signal is via the green/purple wire (terminal C). make sure this wire has a good clean connection at the disconnect plug. In my automotive experiences, a faulty crank position sensor is the number one reason for an EFI engine to simply shut down. Although i have been lucky and never had a fuel pump failure, I would suspect the fuel pump failure to also cause a shut down scenario. Unfortunately, the PCM TBI system does not simply have a CPS to replace as it is part of the interupter/trigger/distributor. Also, once the engine shuts down, you should be able to cycle the ignition switch and hear the fuel pumps run for several seconds. If you do not, then focus on the pumps and related electricial components. And, do not forget about that 15 amp breaker! I suggest you simply bypa$$ the breaker during testing. (the 15 amp breaker with the red wire feeds the pumps and ECM via the 60 amp breaker). Or, you can check the breaker by looking for 12 volts (key on or off) at terminal #30 of the ECM (check after engine shut down...ie hot). Terminal #87 (yellow wire) of the fuel pump relay is the 12 volt (+) terminal. The injectors get power via the fuel pump plug terminal #87 (red wire) not the relay terminal. So, check the connection at the fuel pump because even if the pumps run, the injector power circuit could be cutting out. The ECM just completes the injector circuits to ground. I know this post is a little disjointed, but I was typing as I was thinking and reading. Hope it helps. ------------- |
Posted By: kevman38
Date Posted: September-05-2006 at 10:41pm
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well..... I found my shop manual!!!! Intermittent electrical problems are the hardest. I believe it is the 12.5 amp breaker.When metering to ground I was only getting 3 volts IE. no power to ECM or fuel pumps.It's a little late to run her in the drive way ,but after jumping through breaker I had zero power failures out of about 20 try's. If the diagnosis is correct , I'll be replacing the 60 and 15 amp breakers as well. I'm not claiming victory yet as the preverbal "fat lady" has not sung.
Stay tuned. Kevin |
Posted By: The Dude
Date Posted: September-06-2006 at 12:30am
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Here's to the fat lady singing loud and long. ------------- Mullet Free since 93 http://www.correctcraftfan.com/diaries/details.asp?ID=717&sort=&pagenum=1&yrstart=1991&yrend=1995 - 95 Sport |
Posted By: David F
Date Posted: September-06-2006 at 9:55am
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The breakers! I think you found the problem. Just as in my case (faulty ground) it is usually a simple problem. It makes you wonder how many perfectly good TBI systems have been junked for simple and unrelated failures. I am happy you stuck with it and did not give up. ------------- |
Posted By: kevman38
Date Posted: September-06-2006 at 10:27pm
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Well did my drive way test.......and I'm sick ! Started fine ran 5 min blah blah blah same story. New ignition switch , fuel pump relay ,jumped 12.5 breaker, tried new ECM and pro tech coil pack. The only thing consistent is heat. I'll look at all the pins and connections again for 12 volts to the pumps and ECM.It has to show it's self. Did I mention that I hate intermittent electrical issues.
Kevin David, thanks for you help.I may call on you again if thats ok. |
Posted By: David F
Date Posted: September-07-2006 at 8:53am
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Well Kevin, I am running out of ideas. You definately need to determine if the problem is fuel or electrical related. When running watch the injectors until the engine quits. Do the injectors stop spraying fuel or does it quit while fuel is still being delivered. Next check for spark at a plug after it quits. Then you can focus your attention.
I suspect electrical (not fuel) as you do. Start at the battery and check/clean all connections. Do not skip over fuse holders/fusible links/etc. along the way. Going from memory, there is a seperate hot wire from the battery (not the starting cable) that has a fuse holder. Check it for cleanliness. Again going from my poor memory. If I have time tonight, I will go through my engine and try to think what could be causing your problem. this will refresh my memory on what to look for and what does what. Do NOT give up, we will get it running. ------------- |
Posted By: David F
Date Posted: September-15-2006 at 9:22am
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Status? ------------- |
Posted By: kevman38
Date Posted: September-19-2006 at 9:41am
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Well for inspiring minds that want to know....The conclusion.It was the wiring harness extension from the dash to the engine. The purple wire from the ignition that powers the pumps was bad ,but not quit bad. The wire has continuity ,but when heated (carrying voltage or ambient) would reduce the voltage to 3 volts or less.I have not striped the insulation off to see the affected area ,but am looking forward to cutting it up into little bitty pieces. Total cost 80.00 dollars for the harness 500.00 for anger management therapy. Thanks for all of your help this is a outstanding resource for correct craft owners.
Kevin |
Posted By: David F
Date Posted: September-19-2006 at 10:00am
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Well, great news. I hope you have it nailed this time for sure. A good lesson/reminder to all of us that wiring can/does fail. Problems within the wiring (not connectors) are the hardest to find. ------------- |