Running rich
 

I thought I would ask if anybody knows a direction I need to go. 1995 454 MPI 385 HP. Runs rich. After it is up to temp if I shut it down for a little while I have too bring the throttle up to half throttle for the engine to start. I was told that shuts the fuel injectors off. I pulled all injectors and had them checked. Replaced the bad ones. Also had to replace coolant temp sensor. Any help is greatly appreciated as you can imagine the soot on the transom (not to mention the odor at idle). Don't know that it matters but the boat is a 1995 29' Fountain w/ twins. Thanks again in advance Gil.

Re: Running rich
 

Scan the ECM for a trouble code. The temp sender may be sending the wrong info to the ECM.
With two engines it's easy to switch one component at a time to see which one makes the problem jump over to the other engine.

Re: Running rich
 

No codes. Temp on scanner read 119 through the sender. Never got over that.

Re: Running rich
 

Sounds like injectors are leaking when off. If you are able to watch your fuel pressure during a shut off condition, this will help tell you if this is happening. Fuel cut off usually does not occur until full throttle during cranking (at least wich cars, not sure with boats). A coolant temp sender which reads way too cold could cause it, but would have to be stuck at cold which should trip a fault code. There are no fault codes for leaking injectors. Also check the fuel pressure regulator if it has one. Vacuum test it to make sure the diaphram is not leaking fuel into the intake system. Could also just pull the fuel pressure regulator vacuum hose and see if it is wet with fuel.

Re: Running rich
 

I agree that the temp sender is reading way to cold. I would definetly look into that. Here is another possibility....Do your motors have a VST tank? If so, it can cause this problem. I did a search for VST and came up with this thread. It may help you. There are a few others if you want to check them out.

http://www.offshoreonly.com/forums/s...&highlight=vst

Re: Running rich
 

Yes, check the fuel pressure. If the screen under the regulator is clogged, the pressure will be much too high for the injectors to hold fuel back.

119 sounds way too cold for an engine that has a 165 thermostat.
Sounds like the sender is faulty.

Re: Running rich
 

Thanks for the info guys. I have to get this fixed :hothead:.

Re: Running rich
 

Could quite possibly be a bad stat too. seens lots of em with impeller pieces wedging them open.

Re: Running rich
 

first thing I would check is the VST tank, If the diaphragm in the vst tank has pin holes in it it will allow enough gas to dump into the #7 cylinder to stop the engine from warming up properly. That will also cause the ecm to stay in enrich mode because the motor is running cold which compounds the problem. Pull the hose that runs to the intake manifold and see if there is gas in it. If there is then the vst tank is the problem.

Re: Running rich
 

Do you have the second fuel pump on the sea water pump?

Re: Running rich
 

Yes I do.

Re: Running rich
 

If the temp is only getting to 119 then it's never getting out of cold start enrichment. Fix the temp problem and it will solve the rich problem. Probably a stuck thermostat if it won't heat up. If the reading is in error then it has to be the sender. Keep in mind the sender for the ECM is not the same one for the gauge, so the gauge can read something different than what the ECM sees. It must get over 140 to get out of cold start enrichment.