Loss of Power 97 454 xli

One of my 97 454 xli's &#4

One of my 97 454 xli's (fuel injected) is loosing power infrequently. The motors idle fine but every once in a while they loose rpm's when increasing speed or at cruise. I have noticed a lot of similar problems in this site but never found a post with specific problem. Has anyone experienced the same and found the problem?

thanks

dave

"Try looking at the particulat

"Try looking at the particulate filters. I have a 350xli and found that the large screen like filter was full of large junk filtered from the gas. I used 3M brake cleaner, (did not want to melt the rubber gasket), to remove the junk on the filter. Replaced and saw a dramatic increase in power. Took about 20 minutes total for both engines. NOTE: be sure to shut off or plug your gas line from the tank so that you are not leaking gas into your bilge."

i have the same problem with m

i have the same problem with my 270 crusader. i just found out from a friend to check the vacumn hose leading from the manifold to the carb. when you increase rpm's the vacumn increases as well. if.....your hose is old it can calaps on itself preventing timing advancement to work properly. i don't know if it will work or not as i'm away from my boat but it sure sound's like a good place to look.

"454 XLI does not have vacuum

"454 XLI does not have vacuum advance, but filters is always the first place to look. In your situation Dave, it could be anything from a bad plug or cracked cap to water in the fuel. Follow CK's advice and check ALL of the filters, not just the ones that are easy to get to. If everything looks good, move on to the next possibility, ignition, vacuum leak, etc.

Good luck
Rick"

"Thanks for the advice. The i

"Thanks for the advice. The interesting part is that my boat was just in for brand new gas tank, new racors and new secondary and particulate filters. The problem occurred 10 minutes from the dock on the first tank of gas in that tank and filters etc. I also replaced the coolant cap and had the plugs and timing checked with no obvious problems, compression was also checked and ok.

I am stuck and not sure what to look for next. What else could cause a loss in power?

Thanks again for all the help.

Dave

I will check the"

"Well, that a horse of a diffe

"Well, that a horse of a different color. Remove and inspect the anti-siphon valves. New tanks are normally shipped with plastic pipe plugs in the fittings to protect the tank from contamination prior to installation. I guess the tank manufacturers don't make enough money on the tanks to use metal plugs (@ .15 ea.). Anyway, the threads from these plastic plugs peel off while being installed and removed and sometimes fall into the pick-up tube. When the engine is started they get sucked up into the anti-siphin valve and cause the ball to stick. It's not stuck closed, but it not open enough to allow for adequate fuel flow under a load. There is a very good chance this is your problem. Remove the valve, plunge it with a screwdriver to make sure it is clean and working properly, reinstall them being sure the ball end is toward the tank and the spring end is away from the tank.
Good luck,
Rick"

"I had this EXACT problem with

"I had this EXACT problem with my Starboard fuel tank. Yes, there were plastic pipe fitting shavings lodged in the anti-siphon valve.

This also presents another problem. The anti-siphon valve is now stuck in an open position, meaning that it's not preventing gas from siphoning out of the tank. Could be a dangerous situation if you develop a fuel line leak."

"I had a very similar problem.

"I had a very similar problem. Here is what fixed mine. I decided to install a test wire harness at the fuel pump to monitor voltage at the pump. After running the engine for a 1/2 hour I found erratic voltage at the pump. Did more checking and found break in the positive wire near pump. Repaired and tested again. Voltage at pump now constant but was fuel pressure would still drop below 15 psi at higher rpms and fuel pressure was erratic at all rpms engine warmed up. As a test I restricted the fuel return hose and fuel pressure shot up, engine ran fine. This engine has three fuel filters.Removed and cleaned the primary filter. Engine is back to full RPM and fuel pressure holds at 19 psi. It had only been five engine hours since the primary filter had been cleaned."

It sounds like you may be havi

It sounds like you may be having a scaling problem. Eeeeks... You better check them again in 5 more.

"Dave, Were you able to resolv

"Dave, Were you able to resolve your problem? I have the same engine, no new fuel tanks though. My Starboard engine is exibiting the same symptoms. I've done a complete tune up (plugs, wires, cap, fuel filters etc.)Also replaced the fuel pump, mechanic tells me he pressure tested it and got 19psi. (at the dock) Mine seems to be related to either time or temperature (if I cruise at 1800 rpm it starts happening in about 1hr if I throttle up to 3800 rpm it only takes about 10 min)Man i'm lost with this one. Where are the vacuum lines on this engine that would affect this?"

If you remove the spark arrest

If you remove the spark arrestor on the back side of the throttle body in the middle is vacuum line.If you disconnect it the engine will run rough and it will store a code. I recommed connecting a fuel pressure gauge.They cost less than $50.00. Pressure should stay steady at all rpms. If it drops slightly pinch the fuel return line. You should see pressure increase. Use caution. When I did this it spiked to over 60 psi. If you can keep pressure above 15 psi the engine should run good. If this works you need to replace fuel filters. Mine has three. They primary filter on the later version xli can be cleaned with soap and water.