PDA

View Full Version : HELP- No power to fuel pump relay 94 PS205 350


Grassmankev
08-04-2011, 11:40 PM
Please help! I recently had a problem where my engine on my 94 ProStar 205 with 5.7L TBI wouldn't start back up after about an hour of running. Checked on it the next day, and it fired right up. The next afternoon, when pulling some kids it died again. Fuel pump wasn't coming on, not even to prime (initial 2 sec. burst like normal) Then it would work sometimes. no rhyme or reason as to when it would / wouldn't work. Also noticed a very high idle rpm (1200-1800rpm). I replaced the fuel filter but problem returned within 30 min. I have power to the ignition, good fire at the coil, but when it doesn't work, I don't have 12 volts at the fuel pump. I replaced the fuel pump relay but still no fix. I traced power from all over the place. I have good ground, 12v from the purple ignition wire, 12v on the pink wire going into the fuel pump relay. I DO NOT get 12v on the green/white wire going into the fuel pump relay from the ECM. From what I've seen, I should when I try to start it. No matter what I do now, it won't start- no power to the pump. Is my ECM bad, or could it just be a sensor somewhere not allowing the ECM to power the green/white wire for the relay? Please help, I'm out of options! Thanks

j.mccreight@hotmail.com
08-05-2011, 12:08 AM
Barring your kill switch or neutral safety switch on trans is not bad

at the fuel pump relay
pin 86 black/white is constant ground
pin 30 pink switched 12v from fuse
pin 87 grey supplies 12v from relay to fuel pump
pin 85 green/ white voltage from ecm

basically if your not getting voltage from the ecm to the relay on the green wire the driver in the ecm is bad and needs to be replaced, barring you don't have a broken wire some where.

for diag. you could remove the relay and use a jumper wire to connect the pink wire to the gray wire and see if the pump runs when trying to start.

Thrall
08-05-2011, 02:26 AM
It's not common, but it happened to me...a fried ECM on my '96.
Similar symptoms. Only happened once the engine got good and heat soaked. The hotter it was, the quicker it would die, then it would restart after sitting with the engine box up for a while (scratching my head and pulling on wires!:confused:) or the next day and run for an hour +/- before problems again.
Traced it to a bad fuel pump driver in the ECM (with help from the dealer and Indmar, AND JimN ! was over my head once I eliminated every other possible cause but the ECM).
May have trouble locating one with MEFI III programming. I had to buy a re-furb one back in 04, or go to a newer MEFI IV ECM with some new wiring required.
If your ground is good to the fp and the relay is replaced and you've traced that you're not getting signal to the grn/wht wire (4-5V I think), and checked the connection at the ECM, ground of the ECM, etc, you may have cooked it somehow.

Grassmankev
08-07-2011, 02:24 PM
Thanks for the help guys. I bypassed the cut off switches and still no luck. My fuel pump still doesn't come on. I removed the relay and jumped between the pink and grey wires. The pump comes on when I turn the key to on and it stays on. I'm guessing the relay is what helps control the 2 second priming. When I turn the key to start, no fuel comes through the injectors. I don't have 12v on those wires during the starting, meaning no fuel to the injectors. Are there any other switches / sensors that could be bad, telling the computer to not power the fuel pump? Really need some help with this one. We have a church youth camp starting in 3 days on a house boat and this is our only towboat. Looks like we may be renting a 12 ft jon boat for tubing!!! Thanks guys!

Grassmankev
08-07-2011, 02:45 PM
One other thing I just noticed... When I check voltage on the system I get 12v when the key is on. When I try to start I get 9v (+/- 1) on the pink wire heading into the fuel pump relay. I checked voltage even back at the starter solenoid and again, around 9v under starting load. I put my battery on charge Friday because I new all of the cranking while troubleshooting would run it down. It's not sluggish turning over, just a little low on the meter. Thought that info may help. Thanks.

mtajpa
08-07-2011, 03:25 PM
Did you check all of the fuses, Quote below is from the Indmar manual. I have a diagram but it is for my 99 LTR. I'll attach it any way may be it will help.

""In addition to the 50 A Circuit Breaker, EFI
Engines are equipped with additional component
overload protection:
Fuel Pump - 15 A ATO Fuse
Injectors - 15 A ATO Fuse
ECM - 15 A ATO Fuse
Figure 6.11 ATO Fuse
EFI fuses are located on the holder (2, Figure 6-10)
attached with the ECM. To remove or inspect a fuse,
remove molded plastic cap from fuse holder/base.
Inspect fuse and replace if it is defective, (Figure 6-11).""

j.mccreight@hotmail.com
08-07-2011, 03:40 PM
9 volts is a problem.

mtajpa
08-07-2011, 04:45 PM
One other thing I just noticed... When I check voltage on the system I get 12v when the key is on. When I try to start I get 9v (+/- 1) on the pink wire heading into the fuel pump relay. I checked voltage even back at the starter solenoid and again, around 9v under starting load. I put my battery on charge Friday because I new all of the cranking while troubleshooting would run it down. It's not sluggish turning over, just a little low on the meter. Thought that info may help. Thanks.

9 volts would be a problem sounds like a bad ground unless the battery is failing under load. If it is cranking ok are you sure you meter has a good ground. Check the voltage right at the battery when the starter is turning over. If you are getting 9 volts then your battery is shot. Bad connections show up under load better than just reading the static voltage.

Grassmankev
08-09-2011, 06:08 PM
Thanks for all the tips guys. I tried a new battery and still nothing. After checking with Indmar, they told me the ECM is done. Unfortunately, they don't make the MEFI 1 or 2 any longer. Rather than trying to find a refurb or something, they told me I can just install an oil pressure switch that will send 12v to the fuel pump relay. I cut the green/white wire where it comes out of the ECM and wire it into the pressure switch. The other terminal on the switch is wired to ignition + and when it senses around 6 psi or so of oil pressure, it powers the relay. A $25 part!! Apparently, this is how MerCruise has been powering fuel pumps for a while now. Gonna hook it all up and give it a try tomorrow. Fingers crossed, but it all sounds good. I'll let you guys know how it turns out.

ahhudgins
08-09-2011, 07:20 PM
When you say it "dies" do you mean it actually cuts off when it's running or it just won't restart after you cut it off?

Some of us with 95's have found out that if the engine temperature gets too high (but not enough to cause an alarm) the engine will crank but no restart until it cools down. If I (and others) install a 160 degree thermostat in place of the 143 degree, this happens more often, so we leave the 143 thermostat in the engine. This leads me to believe that the ECM is looking at the engine temperature sending unit and not allowing the engine to fire up. So, a bad sending unit could cause your problem, but I don't know what functions the ECM cuts off when this happens.

My 95 also would not restart because I had a bad ignition switch, but if you are 100% sure you have 12V at the pink wire to the fuel pump relay, then the IGN contact on the switch is working. As another posted stated, I would check into why you only have 9V!!! Is the new battery dropping to 9V or is the 3V being dropped at a connection? If the battery is staying up but you only have 9V to the fuel pump relay, you could have a faulty MEFI system relay or a bad connection. I would hate to do the rig job if you have a simple connection issue.