1995 Mercury 200 XRi - Hesitation when getting on plane

[deesel104]

1995 Merc 200 XRi - serial # OG178803

The motor is on a 19' bass boat. Have been fighting multiple effects throughout the spring and could use some help finding root cause.

I initially had an issue where boat would only idle and would die while running. My mechanic initially found a cracked mid-section housing and blown exhaust gaskets which he replaced with a mid-section he had from a 175 XRi and fresh gaskets. He also said I had two cracked coils that he replaced. I noticed an immediate improvement in low-end power but still had the issue where the boat would shut off after running for a minute or so.

I took it back and he found deteriorating fuel lines. I was surprised since I had replaced them about 6 years ago with ethanol-approved lines, but he showed them to me and they were indeed bad as the inner liners were separating from the housing but not brittle/breaking. He replaced all fuel lines but DID NOT rebuild the pulse fuel pump or replace the water separator filter since I had done those about a month prior. The boat performance immediately improved. The first 4 or 5 attempts to get on plane were full power but on the next attempt and all subsequent attempts (consistent for last 2 - 3 trips) it hesitates when getting on plane. It seems to bog like its down on power and then it will finally kick in and go once it starts to get to fall over onto plane. Once on plane it seems to be fine at mid and high rpms - runs great at around 5500 - 5600 rpm. One point of note is it always hesitates when motor is down for launch but doesn't seem to do it if I power load on the trailer with motor trimmed slightly above level - not sure if that is relevant but wanted to note it. Also wanted to note that 1st crank of the day it always starts up and revs strong. Subsequent attempts to crank I usually find the primer bulb empty and even after pumping it is difficult to start and acts like it is starving for fuel. Seems to crank better if motor is slightly above level trim but I always pump bulb, wait for 10-20s after key turned ON, and then try to start. It usually acts like it is starving for fuel. I had some time this weekend so I decided to do some troubleshooting myself.

I performed a fuel pressure test and found a few things. Results are below:

• key in OFF position with bulb firm: 0 psi
• key in ON position with electric pump running (~20 s): 39 psi
• 10s after Epump turned off: 15 psi (I'm assuming this is incorrect so something isn't holding pressure - true?)
• 20s after Epump turned off: 10 psi
• idle speed (~750 rpm): 36 psi
• under accel (up to 2000 rpm): 36 psi
• 15s after shutdown: 10 psi (again I'm assuming this is a problem)
• 30s after shutdown: 5 psi
• 60s after shutdown: 0 psi

I removed the final filter and confirmed that it was clean. I also removed the fuel pressure regulator but noticed the small filter that is supposed to be in that regulator isn't there. Don't think this is my problem but I'm assuming that needs to be there - where can I get one? I then performed the fuel pressure regulator test where I turned the key with the regulator held into a glass jar and it shot fuel when key was on and immediately stopped with key was turned off. Fuel looked like good/clean oil/fuel mixture.

I do have a pulse fuel pump rebuild kit and water separator filter on order but delivery has been delayed. I plan to install those to rule out any residual effects from the bad lines as it should have been done all at once from what I'm reading.

Can someone please advise what I should do next? I'm thinking the fuel pressure loss after the Epump turns off and immediately after shutdown is indicative of the issue.

I appreciate any help you can provide.

[JOE54]

may have debri in regulator from screen being gone causing fuel psi dropping so quickly

[deesel104]

As per above, I tested the regulator by testing it unattached from the VST. When key turned strong stream of clean fuel/oil mix and quickly stops after key turned off. Fuel/oil mix captured in a jar looked good with no debri, water, or otherwise. Would that not confirm regulator is OK? Is there a better way to test?

[JOE54]

pinch off hose to reg pressure up system see if it still falls as quickly= leak in inj housing

[deesel104]

Makes sense - thanks Joe. Will report back with results.

[deesel104]

I was able to pinch off the hose between the final filter an the injector housing (labeled "1" in image) after the pump cut off and it held pressure as soon as pinched. I then re-tested but pinched the hose between the regulator and the injector housing (labeled "2" in image) and this also held pressure. Does this signal leakage in the injector housing or the regulator?

[JOE54]

REG

[deesel104]

Joe - based on your suggestion I targeted the regulator again as I didn't understand why I thought it passed the original jar test. I repeated the test but this time used a clear jar that was large enough to see more clearly when I turned off the key and propped it up so I could see it from the ignition switch at console. I saw that when the key was turned off the regulator does drip a small stream of fuel as it bleeds off the fuel pressure. I didn't notice this the 1st time I did the test because I was going back and forth between the jar and the console, but this confirms regulator issue. It doesn't take much of a leak to bleed that pressure pretty quickly. I've got a new pressure regulator on order. Many thanks for the help!

(If Don's reading this - thanks for the discussion over the phone Don. I bought the air chucks and an inner tube repair kit but didn't need them after all!)

I will advise if I have any further hesitation issues once the new regulator is installed.

[JoeBass1986]

Pressure regulator inside the VST? Is that the tall pump or the block float? Is the float supposed to make a noise when metal to metal like the pump does when I turn my key over or no?
Mine stalls sputters and dies if i trim down.. Won't crank unless halfway trimmed up or higher. My bulb doesn't go flat but I can usually pump it back full after a few mins. How long should it stay full?

[deesel104]

Pressure regulator inside the VST? Is that the tall pump or the block float? Is the float supposed to make a noise when metal to metal like the pump does when I turn my key over or no?
Mine stalls sputters and dies if i trim down.. Won't crank unless halfway trimmed up or higher. My bulb doesn't go flat but I can usually pump it back full after a few mins. How long should it stay full?

JoeBass1986 - if you look at the picture I attached the fuel pressure regulator is the canister that is connected to the fuel line I labeled as "2". It has the small vacuum line attached at the top. Regarding your problems, I suggest checking out the FAQ ("Sticky" at top) and looking at the "fuel related problems" section. I suggest starting a new thread with your engine serial # so you can get better assistance. I also recommend starting with the basics assuming you have same engine as em (fuel lines, pulse fuel pump diaphragm, water separator filter, and fuel pressure test).

[JOE54]

yep need hp and ser number please

[deesel104]

So I replaced the fuel pressure regulator and have confirmed I now have good fuel pressure. 39 psi with key on and holds 35 - 36psi for a good while after turning key off, as expected. I took the boat out this weekend to test it and still haven't fixed my hesitation problem. It idles fine and runs WOT around 5600 just fine, but really hesitates getting on plane. It seems like it is missing, bucks a few times, then will get on plane and run great. The only time I notice the hesitation is trying to get out of the hole.

I have dual tanks and confirmed it hesitates on both tanks. Some have suggest fuel tank vents so pretty sure that eliminates this as an issue.

What should I test next? I'm thinking I'll take the fuel pressure gauge with me to the lake and watch fuel pressure during the hesitation to see if there is anything iffy there. Otherwise thinking this may be electrical. I appreciate any help.

[deesel104]

UPDATE: After going through the fuel system I started diagnostics on the electrical system and found my gremlin. I had a coil wire that was on the lug with no nut, conveniently hidden by the rubber boot. I fixed the oversight and now she runs smooth under acceleration.

It is still difficult to start, which doesn't seem right for an EFI. Fuel system seems good to go - where should I look to improve the starting? I'm pumping bulb firm each time and allowing the electric fuel pump to run 10-20s before trying to crank it.

I had Don do the injectors a while back, but thinking that's been 6 years or more. How difficult is it to remove the intake to get that done? Does it require a Sync-n-link after?

[JOE54]

testing all sensors and switches ,somewhat entailed to remove ,and yes it will need sync