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8.1 no spark.

J

JEJ

New member
New to this forum. I rebuilt two 8.1 MPI Crusaders. Starboard runs perfect. Portside had some idle issues so I put in new throtle position sensor and new Idle control sensor. Now I have no spark. I cant run the motor to get a reading on my scaner however prior to changing sensors, MAP sensor came up. Dont think that would stop spark, ANY IDEAS ?

THANKS.
 
What I would do is put the old sensors back in and see if the engine runs. If it does, then just replace one at a time to see if perhaps one of the "new" sensors is causing the problem.
 
erich, I appreciate the response. I will give it a shot the next time I get to the boat. Unfortunatly I live 6 hours from my boat, so it's going to take a while to respond back to your suggestion. I only get to see my precious every other weekend. Thanks again.
 
Idle air motor and MAP should not have any effect on spark...Do any of the coils fire?

Any chance you disconnected a connector elsewhere in the harness while changing your sensor/IAC?

Did you change the relays when you did the rebuild...they don't last forever...

If you are certain it is lack of spark, I'd suggest focusing on lack of trigger or lack of the 12VDC source...
 
Mako is right (as usual), what you changed would not affect the spark. But obviously something wiggled, or was bumped, or just happened to fail at that moment. And your original idle issue would not have been affected by the throttle position sensor (good or bad), which suggests that while you have the scanner you don't have the MEFI manual. Without a good understanding of how the system functions you are going to struggle (do an internet search to find a manual , they are out there for free and for pay). Sounds like you may have a connection problem (since it did run before). Or the crank sensor. Or your Cam Retard setting (changed by loosening the distributor and rotating) is way off, and if the bolt is not tight maybe moving farther off.

If you crank the engine after giving it a good shot of starter fluid, that will tell you for sure if there is any spark there. If it does not fire, check all connections and then start down the path laid out in the manual. Or start swapping likely suspects with the good engine. Also, even if the engine does not run, you can use the scanner so see if any codes have been thrown. For example if your crankshaft sensor is bad or disconnected your scanner will tell you that.

Good Luck,
CaboJohn
 
I appreciate the responses. I'll be heading down to the boat this weekend and will give an update when I get back. I have all the manuals, looks like I'll have a lot of reading to do. Thanks again.
 
Not to piggy-back on this thread but I will soon be getting a boat with 2003 Crusader 8.1L engines and would like to get the service/repair manual for them. A Google search didn't seem to help much. Where is a good place to get that manual. I was able to download the Owner's Manual and Parts Manual and assume the Repair manual will have to be purchased...but where?

Thanks,
 
The diagnostics "manual" is for the MEFI (engine computer) and runs about 350 pages for the MEFI 4 and over 400 pages for the MEFI 5 (you will need to print double side and use a big binder!). So start your search using the term MEFI. I don't know whether the 8.1L uses a 4 or a 5. Serial numbers are on the bottom of the ECU, and the 4 and the 5 look different so if you look at the drawings in the manual and then the actual unit it will be obvious. The hot rod community loves these Marine Electronic Fuel Injection engine controls and have posted a lot about them. The web site Pirate 4x4 has a good article on the MEFI 4 and a link to the manual. I have seen links to the 4 on other sites as well. A quick search a moment ago popped up the complete MEFI 5 manual in PDP format about the 4th item down so it is not hard to find.
CaboJohn
 
Cabo,

As you suggested I did a few searches and found some posts that say the Crusader 8.1 has a MEFI-4 computer. I also found the manual. Thanks for your good advise.

Erich
 
To whom it may concern, HELP. Its been a while since I've gotten to my boat and I have taken all suggestions to try to fix the no start issue. I'll give you some background on my 2001 8.1 Crusader. MPI Captains Choice. I re-built both motors. All was going well and for some reason the pig tail on my Fuel Control Cell (FCC) just fell off. I was able to find an after market pig tail and install it. Once Installed, I now can not start motor. The motor still has a strong crank but no start. It acts like a fuel issue, so I took off the FCC from the other motor as well as the Map and crank shaft sensor. Still no start. I had just installed new idle control sensor and throttle position sensor. I've checked all fuses, all sensors and It still wont start. If anyone can help, it would save me from donating the boat to the reef fund.
 
Did you do the test with starting fluid? If the engine kicked over then you correct, it is most likely a fuel issue. If not, it is most likely a spark issue.

If it is a fuel problem as you believe, you need to determine if you have pressure in the fuel rails. There is a fitting under a cap on the rails that looks like a large tire valve. That is where you attach the fuel pressure gauge. If you do not have a gauge, you can turn the ignition on for several seconds and then turn it off. That should pressurize the rail. Use a small object to depress the pin in the middle of the fitting and you should get a squirt of fuel (use a rag to keep it from going everywhere, particularly in your eyes). If you get the squirt you have pressure, if not, you don't. When you lost your pigtail you likely blew a fuse. If you unplug the fuel pump you can check the voltage being supplied to the pump at the plug once the ignition is on (it will only be there for the first few seconds and then turns off if the engine does not run). If no voltage I believe that the fuses are in those things the look like large unused plugs on top of the engine, covered with caps. They contain fuses and relays and the reason for lack of voltage may be there.

If that is not the issue then maybe the computer is telling the fuel pump not to turn on (and will also tell the ignition not to fire). But those things should throw a code, and it can be read even if the engine does not run.

If you can't read the computer, then maybe it is not getting power (even though the starter is). Look in the manual to see which terminals in the computer plugs should have 12v and see if it is there. If you don't have juice use a meter to chase it down.

Since you have a good engine next to it, you will eventually find the problem. But you are much better off narrowing it down before you continue the parts swap.

CaboJohn
 
Cobo John, thank you for the reply. Yes, I did check the fuel rail valve and I do have preasure, not what I'm accustome to but its there. I depress valve once and then the preasure is gone. I did swap FCC from other motor and still have same preasure. I did get a code 34 low voltage to MAP sensor. I swaped MAP sensors from other motor and still no start. I checked the fuses and all good. My next try is to swap MEFI's. I just dont get why I'm not getting a spark. I am really really frustrated.

JEJ
 
The fuel pump only turns on for 2 sec. to pressurize the rail and then shuts down unless you have engine start. One squirt is all you will get in your test and then the rail is depressurized. So that sounds correct. Perhaps someone on this site will advise you of the best, most methodical way to run down lack of spark. Or you can just keep swapping. And check your plugs again. The ones that matter for spark are the crank sensor, the one going into the base of the distributor, the two into the coil, the two into the computer, and of course the coil to distributor wire. MAP will not matter.

Are you sure your distributor is in correctly? Maybe you are off a tooth (or more).
 
A scan tool will give you valuable information, even without the engine running.

What fuel pressure is in the rail?

You never mentioned verifying the relays are functioning...did you check them? the fuel pump relay is usually fed from the system relay...the ignition is fed from the system relay as well...do you get +12VDC, at the ignition coils, with the key on???
 
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