Damn fuel injection! Help!
07-07-2013 | 10:08 AM
#1
Thread Starter
Registered
Joined: Feb 2005
Posts: 42
Likes: 0
From: Southern Marylend
Damn fuel injection! Help!
I’m battling a nasty fuel system problem that seems to stem back to some bad, separated ethanol fuel. I’d like to see if anyone has any suggestions. Here’s the history:
I have a 95 Formula 252LS with a 7.4L Mag EFI. The boat was running wonderfully last year and I was happy as a clam. Super Storm Sandy was heading up the east coast and I pulled the boat out and let it sit on the trailer (it usually sits on a boat lift on my pier). I figured that would be the end of my boating season and planned to go ahead and winterize it at some point. Well about a month later we got a warm spell so I figured I’d splash her again and burn out some of the old gas. When I launched I found the engine running real rough. I was still in one of the back creeks so I didn’t even try to get her up on plane, but just idling down the creek I knew something wasn’t right. So I turned around and put in back on the trailer and down to the local shop. They told me my fuel had separated. They ran it on fresh aviation gas to winterize it, and told me I’d have to pump out the remainder of the gas in the spring.
Fast forward to spring. Over the winter I did some research on ethanol gas and the pros and cons. It’s actually a pretty good fuel in small quantities over a short length of time. Its hydroscopic properties are actually pretty beneficial. To a point. It can absorb some of the condensation in the tank and burn it out. If, however, you get too much moisture the ethanol will separate from the gasoline, and then you’re screwed. So anyway I rig up a fuel transfer rig and pump out all the gas right from the fuel pickup on the tank. I pump out about 35 gallons. 10 of which I pumped into my truck and it ran great (but it was likely the gas-only layer). I head to the gas station and put 40 gallons of fresh E90, again assuming that this fuel might actually absorb some of the left over crap that didn’t pump out. I splash the boat, fire her up, and head down the creek. She’s idling great. I’m thinking I’d golden. Then I get to open water and crack the throttle. Boat just about gets on plane and then dogs. Doesn’t completely stall but completely loses power. Doesn’t run rough or stammer. It just falls flat on its face. Tried it a dozen times and it was completely repeatable. So back on the trailer and back to the shop.
They changed the plugs, cap, wires, all of which I knew was a waster because I’d just doe that about 20 hours before. That didn’t help. The mechanic starts talking about clogged fuel injectors. That’s plausible but it seems to me that a few bad injectors would make the engine run rough not die completely. It feels like the engine is fine but the fuel system just can’t supply enough fuel for high power. They put another mechanic on it and he diagnoses a bad fuel pressure regulator. THAT to me sounded right. So they pull the EFI plenum and replace the regulator and take her for a sea trial. Boat pulls like gangbusters. I pay my $3000 bill and hit the water. Boat runs great. Did several full throttle runs and had no trouble sustaining 4200 RPM and 56 MPH on GPS. I was happy…. For about 3 hours run time. Now, after about 15-20 minutes I can’t sustain speed. I’ll be cruising along at 40 MPH and she’s lose power again. Still seems to me to be fuel related because it will do it more quickly at high speed than low. I can pretty much hobble around at 30 MPH and it will only dog once or twice, but the higher the speed the more it will choke. I listened carefully during a couple of high speed runs and it almost feels like its running a little rough just before it dies. Sometimes it will stall completely and sometimes I can snap the throttle back to idle in time to catch it. I have yet to have a problem restarting. Just can’t run at power.
I know the mechanic is gonna start pushing the fuel injector bit again, and if he convinces me that a few clogged injectors could cause this behavior great, but it still doesn’t seem to fit. I come back to my thoughts that bad injectors would make it run poorly most if not all the time, and would make the engine run rough. Not die. Also, if the injectors were clogged why would I get great performance for 3 hours and THEN start crapping out? I’ve put 5 cans of sea foam in with ½ tank of gas and been running it around. I think I sense a slight improvement but it might just be my imagination.
Got any ideas? I’m seriously thinking of tanking the EFI for an old fashioned but reliable carb!
I have a 95 Formula 252LS with a 7.4L Mag EFI. The boat was running wonderfully last year and I was happy as a clam. Super Storm Sandy was heading up the east coast and I pulled the boat out and let it sit on the trailer (it usually sits on a boat lift on my pier). I figured that would be the end of my boating season and planned to go ahead and winterize it at some point. Well about a month later we got a warm spell so I figured I’d splash her again and burn out some of the old gas. When I launched I found the engine running real rough. I was still in one of the back creeks so I didn’t even try to get her up on plane, but just idling down the creek I knew something wasn’t right. So I turned around and put in back on the trailer and down to the local shop. They told me my fuel had separated. They ran it on fresh aviation gas to winterize it, and told me I’d have to pump out the remainder of the gas in the spring.
Fast forward to spring. Over the winter I did some research on ethanol gas and the pros and cons. It’s actually a pretty good fuel in small quantities over a short length of time. Its hydroscopic properties are actually pretty beneficial. To a point. It can absorb some of the condensation in the tank and burn it out. If, however, you get too much moisture the ethanol will separate from the gasoline, and then you’re screwed. So anyway I rig up a fuel transfer rig and pump out all the gas right from the fuel pickup on the tank. I pump out about 35 gallons. 10 of which I pumped into my truck and it ran great (but it was likely the gas-only layer). I head to the gas station and put 40 gallons of fresh E90, again assuming that this fuel might actually absorb some of the left over crap that didn’t pump out. I splash the boat, fire her up, and head down the creek. She’s idling great. I’m thinking I’d golden. Then I get to open water and crack the throttle. Boat just about gets on plane and then dogs. Doesn’t completely stall but completely loses power. Doesn’t run rough or stammer. It just falls flat on its face. Tried it a dozen times and it was completely repeatable. So back on the trailer and back to the shop.
They changed the plugs, cap, wires, all of which I knew was a waster because I’d just doe that about 20 hours before. That didn’t help. The mechanic starts talking about clogged fuel injectors. That’s plausible but it seems to me that a few bad injectors would make the engine run rough not die completely. It feels like the engine is fine but the fuel system just can’t supply enough fuel for high power. They put another mechanic on it and he diagnoses a bad fuel pressure regulator. THAT to me sounded right. So they pull the EFI plenum and replace the regulator and take her for a sea trial. Boat pulls like gangbusters. I pay my $3000 bill and hit the water. Boat runs great. Did several full throttle runs and had no trouble sustaining 4200 RPM and 56 MPH on GPS. I was happy…. For about 3 hours run time. Now, after about 15-20 minutes I can’t sustain speed. I’ll be cruising along at 40 MPH and she’s lose power again. Still seems to me to be fuel related because it will do it more quickly at high speed than low. I can pretty much hobble around at 30 MPH and it will only dog once or twice, but the higher the speed the more it will choke. I listened carefully during a couple of high speed runs and it almost feels like its running a little rough just before it dies. Sometimes it will stall completely and sometimes I can snap the throttle back to idle in time to catch it. I have yet to have a problem restarting. Just can’t run at power.
I know the mechanic is gonna start pushing the fuel injector bit again, and if he convinces me that a few clogged injectors could cause this behavior great, but it still doesn’t seem to fit. I come back to my thoughts that bad injectors would make it run poorly most if not all the time, and would make the engine run rough. Not die. Also, if the injectors were clogged why would I get great performance for 3 hours and THEN start crapping out? I’ve put 5 cans of sea foam in with ½ tank of gas and been running it around. I think I sense a slight improvement but it might just be my imagination.
Got any ideas? I’m seriously thinking of tanking the EFI for an old fashioned but reliable carb!
07-07-2013 | 12:21 PM
#4
Registered
Joined: Sep 2006
Posts: 1,391
Likes: 0
From: CapeComa,FL
Couple things to check....in order....
By the way....do you have cool fuel?
First, as icu mentioned.....filters.
#2, what fuel pressure at idle, what at w/o
#3, disconnect gas tank vent and blow way from tank with compressed air (shop air at 150psi +)
#4, injectors
The first is easy and cheap....you can handle it. If you have cool fuel, it is inside the unit, not as easy.
If you have cool fuel, it is very possible that it is suffering from restricted flow throuh the unit. A way to test it is carry some cold water ( not ice cold) and pour itnon the cool fuel housing when the issue pops up. If this
helps, you need to have a pro replace the water in and out as well as the plastic manifold that diverts water.
A fuel psi gauge is cheap. Buy one from the local parts house and screw onto the rail. If you see the pressure drop below 30 at any time, you might have a weak pump, one that is suffering from eaten/deteriorated orings inside, or a voltage issue.
As far as the vent, insects love building homes in the vent line. By disconnecting at the tank and blowing away, you can usually clear any obstruction.
Keep us posted...
By the way....do you have cool fuel?
First, as icu mentioned.....filters.
#2, what fuel pressure at idle, what at w/o
#3, disconnect gas tank vent and blow way from tank with compressed air (shop air at 150psi +)
#4, injectors
The first is easy and cheap....you can handle it. If you have cool fuel, it is inside the unit, not as easy.
If you have cool fuel, it is very possible that it is suffering from restricted flow throuh the unit. A way to test it is carry some cold water ( not ice cold) and pour itnon the cool fuel housing when the issue pops up. If this
helps, you need to have a pro replace the water in and out as well as the plastic manifold that diverts water.
A fuel psi gauge is cheap. Buy one from the local parts house and screw onto the rail. If you see the pressure drop below 30 at any time, you might have a weak pump, one that is suffering from eaten/deteriorated orings inside, or a voltage issue.
As far as the vent, insects love building homes in the vent line. By disconnecting at the tank and blowing away, you can usually clear any obstruction.
Keep us posted...
07-08-2013 | 08:29 PM
#6
Registered
Joined: Oct 2009
Posts: 253
Likes: 0
From: burlington, iowa
any old fuel left in tank could have some water. ethanol is big problem here, holley fuel pump to suck as much fuel at fast rate. tilt bow up, let settle and start pumping out to buckets to check for water that settles on bottom. seafoam contains propylene alcohol, it will mix with ethanol and water instead of your gas. compounds problem. pull fuel filters and dump out to container to check for water. they use ethanol to raise octane, when water starts to fall out of suspension. the octane rating goes with it. I have had good luck with quickleen. running ethanol the injectors seem to get dry, i'll mix quikleen/stabilizer/2cycle oil(lucas top end lube) 1 oz each to spin-on fuel filter.
07-12-2013 | 09:19 AM
#8
Thread Starter
Registered
Joined: Feb 2005
Posts: 42
Likes: 0
From: Southern Marylend
Sorry for the slow reply. Damn day job has kept me away...
I'll change filters tomorrow and try blowing out the vent. If that doesn't do the trick I'll get me hands on a fuel pressure guage.
I'm liking the vent theory. On fresh start up it runs great. It's only after 10-15 minutes of run time that the problem pops up. Could be that insufficient venting is creating vacuum in the tank. After sitting for a while the vacuum subsides. I'll try it and report back.
Thanks
I'll change filters tomorrow and try blowing out the vent. If that doesn't do the trick I'll get me hands on a fuel pressure guage.
I'm liking the vent theory. On fresh start up it runs great. It's only after 10-15 minutes of run time that the problem pops up. Could be that insufficient venting is creating vacuum in the tank. After sitting for a while the vacuum subsides. I'll try it and report back.
Thanks
