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mmthorn
09-03-2011, 08:03 PM
My 1998 Maristar just started having a problem where the engine dies at around 2800 RPM. Sometimes the engine will stay running if I pull the throttle back to the idle position. Other times the engine will completely die.

I figured it might be a fuel problem. This boat has an external electric fuel pump (high pressure type with two inlets) that is attached to the engine.

Here are the things I have tried.

- Replaced both fuel filters.
- Cleaned the screen on the inlet to the fuel pump and the screen on the inlet to the fuel pick up tube. Both were clean by the way.
- Added a fuel injector cleaner product.
- Measured the fuel pressure while driving (30 psi per the owners manual).
- Measured the fuel pressure at key on. (30 psi for a few seconds and then drops to zero). Is this correct?
- Replaced plug wires and plugs.
- Checked compression on all cylinders (190-200psi when engine is warm).
- Kill Lanyard is attached.
- Oil pressure seems to run between 40 and 50psi.
- Checked the engine ground. Clean


Any ideas? Does anyone understand how this dual inlet high pressure fuel pump works?

Thanks,

mmthorn
09-03-2011, 08:19 PM
Just thought I would mention that I also hooked up a diagnostic tester and there were no engine codes. The Throttle position sensor checked out with the diagnostic tester also.

mmthorn
09-03-2011, 09:28 PM
And another thing: I replaced the severely corroded distributor cap and rotor. Did not help.

The motor has 515 hours. I have owned since new.

JLeuck64
09-03-2011, 11:49 PM
What's the fuel pressure like when it dies? Still thinking you may have a fuel delivery problem and would like to see what the fuel pressure is like when the problem is present.

FrankSchwab
09-03-2011, 11:52 PM
I don't have any help for you, but I'm real interested in any responses you get.

You've checked everything I'd check.

mmthorn
09-04-2011, 06:23 PM
I just got off the lake. I ran the boat with the fuel pressure gage attached. The gage reads 30 psi before, during and after the stall. The stall is pretty consistent at around 2800RPM. It seems like the fuel delivery system is working fine. I also watched the two injectors on the TBI and they seemed to be fine until the stall at which time they cut back their flow.

Does anyone have any ideas? Could it be something related to the Ignition Control Module or the ECM?

Thanks for reading this post.

Kell
09-04-2011, 07:35 PM
I seem to recall reading here that 40-50 psi at the shrader valve on the fuel rail? Sorry don't have anything to add but I hope you get this resolved.


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j.mccreight@hotmail.com
09-04-2011, 07:53 PM
I seem to recall reading here that 40-50 psi at the shrader valve on the fuel rail? Sorry don't have anything to add but I hope you get this resolved.


Sent from my iPad 2 3G using Tapatalk

I think your thinking of the mcx, op has a tbi

JimN
09-04-2011, 08:42 PM
The pressure in '98 would have been 30 pounds, so that seems OK, although I would look at the anti-siphon valve and fuel pickup tube.

Remove all of the relays and inspect them for corrosion. If the motor box doesn't have good circulation when the temperature cools and warms up, condensation will take a heavy toll. Make sure the grounds on the engine are spotless and there's no resistance between the ground stud and the battery post.

The pressure will drop at key ON if you don't start it because the initial pressure is from the pump priming. Coast Guard regs require electric fuel pumps to stop if the engine stops.

How old are the plug and coil wires?

mmthorn
09-04-2011, 09:38 PM
- The ground at the battery and on the engine look spotless.
- The plugs and wires are brand new. I just replaced.
- I checked the pick up tube and the screen to the inlet of the fuel pump. Both were clean.
- I will check the relays for corrosion the next time I am at the lake.

- Tell me about the antisiphon valve. I haven't checked this out.

JimN
09-05-2011, 01:22 AM
- The ground at the battery and on the engine look spotless.
- The plugs and wires are brand new. I just replaced.
- I checked the pick up tube and the screen to the inlet of the fuel pump. Both were clean.
- I will check the relays for corrosion the next time I am at the lake.

- Tell me about the antisiphon valve. I haven't checked this out.

The aluminum block at the top of the tank, screwed into the black plastic plate, is the top of the pickup tube and the anti-siphon valve is screwed into that, with a male barb fitting on it. The fuel line attaches to it right at the top of the tank.

The battery contacts can look great but still cause resistance.

mmthorn
09-05-2011, 10:10 AM
Thanks Jim, Could you comment on how a defective (gummed up?) anti siphon valve can cause my problem? If I have good idle performance and good performance up to about 27mph (2800RPM) wouldn't this indicate that my fuel line is clean? Do these get partially plugged and then limit the flow rate through the system? If this were the case wouldn't the fuel pressure drop?

Does my engine have a fuel pump relay or a fuel pump fuse? Both?

Thanks,

JimN
09-05-2011, 10:54 AM
Thanks Jim, Could you comment on how a defective (gummed up?) anti siphon valve can cause my problem? If I have good idle performance and good performance up to about 27mph (2800RPM) wouldn't this indicate that my fuel line is clean? Do these get partially plugged and then limit the flow rate through the system? If this were the case wouldn't the fuel pressure drop?

Does my engine have a fuel pump relay or a fuel pump fuse? Both?

Thanks,

It won't allow enough fuel to pass when you need it. It may run OK at lower RPM but if the flow rate isn't sufficient above 2800, you'll have this issue. The pressure doesn't drop until the problem arises, right?

Does your boat have a fuel shut-off? Make sure that's clear and the lever is positioned so it's in line with the anti-siphon. The anti-siphon can become partially frozen and it would usually be due to moisture in the fuel- just another reason to hate ethanol in the gas.

FrankSchwab
09-05-2011, 06:14 PM
[QUOTE=mmthorn;786512I also watched the two injectors on the TBI and they seemed to be fine until the stall at which time they cut back their flow.
[/QUOTE]

I'm guessing that, in our boats, the ECM isn't going to cut back the flow of fuel at the injectors for too many reasons - so if the engine is turning at 2800 and the throttle is open wide, it should be spraying plenty of fuel into the TB. I think (but am no expert) that if you see the fuel flow cutting back at stall, "that's your problem right there", as opposed to it being a result of the stall.

Of course, I'm a geek, so at this point I'd grab an oscilloscope out of the lab, hook it up to the fuel injectors, and see what the waveforms looked like as the engine hit 2800 RPM. If they look just as clean before the stall as during/after the stall, then the ECM would seem to be in fine shape, and I'd guess that you have a restriction in the fuel lines/pump somewhere. If they go bananas, then I'd guess that the ECM has an issue, and I'd go through the wiring for it point by point.

/frank

mmthorn
09-05-2011, 06:26 PM
The pressure reading on the schrader valve is always at 30PSI. Before, during and after the stall. It doesn't twitch one way or the other. Solid 30PSI.

When I checked the fuel pick up screen I also took apart the turn off valve. It was clean....looked like brand new and the lever fully opened and closed the valve.

It just doesn't seem like this is a fuel issue based on my pressure readings.

Thanks for all the ideas everyone.

JimN
09-05-2011, 07:20 PM
I'm guessing that, in our boats, the ECM isn't going to cut back the flow of fuel at the injectors for too many reasons - so if the engine is turning at 2800 and the throttle is open wide, it should be spraying plenty of fuel into the TB. I think (but am no expert) that if you see the fuel flow cutting back at stall, "that's your problem right there", as opposed to it being a result of the stall.

Of course, I'm a geek, so at this point I'd grab an oscilloscope out of the lab, hook it up to the fuel injectors, and see what the waveforms looked like as the engine hit 2800 RPM. If they look just as clean before the stall as during/after the stall, then the ECM would seem to be in fine shape, and I'd guess that you have a restriction in the fuel lines/pump somewhere. If they go bananas, then I'd guess that the ECM has an issue, and I'd go through the wiring for it point by point.

/frank

The injectors see square wave but without knowing the intended pulse width, the scope won't show much, other than gaps that were caused by something else. I would be more inclined to take it in so a diagnostic computer can be hooked up.

One thing I would definitely check is the grounds at the rear of the engine. The fuel pump grounds there and if its ground is flaky, it can do odd things during hard acceleration.

JimN
09-05-2011, 07:22 PM
The pressure reading on the schrader valve is always at 30PSI. Before, during and after the stall. It doesn't twitch one way or the other. Solid 30PSI.

When I checked the fuel pick up screen I also took apart the turn off valve. It was clean....looked like brand new and the lever fully opened and closed the valve.

It just doesn't seem like this is a fuel issue based on my pressure readings.

Thanks for all the ideas everyone.

Disconnect the TPS and see if anything changes. It won't have crisp throttle response but it may have higher top end if the sensor is bad.

mmthorn
09-10-2011, 09:08 PM
I tried disconnecting the TPS. The idle speed increased but the boat still stalled out at 2800 RPM.

mmthorn
09-10-2011, 09:15 PM
This afternoon I "dead headed" the fuel pump. I did this by crimping the return line which restricts the fuel flow (overrides the fuel pressure regulator) and forces the pump to work harder. The pressure measured 60 psi (30 psi is normal). This indicates that the pump is working. I left the return line crimped and accelerated to see if my boat still stalled at 2800. Yep. Still stalled.

I then decided to go for a little cruise at about 2500 RPM and after 15 minutes the boat stalled. It looks like my boat is now stalling at 2500 RPM.

Also, I have been asked by a couple of people to check the anti syphon valve which on some boats is attached to the aluminum block at the top of the fuel tank. My 1998 Maristar 200VRS does not have one.

Any other ideas?

JimN
09-11-2011, 12:05 AM
This afternoon I "dead headed" the fuel pump. I did this by crimping the return line which restricts the fuel flow (overrides the fuel pressure regulator) and forces the pump to work harder. The pressure measured 60 psi (30 psi is normal). This indicates that the pump is working. I left the return line crimped and accelerated to see if my boat still stalled at 2800. Yep. Still stalled.

I then decided to go for a little cruise at about 2500 RPM and after 15 minutes the boat stalled. It looks like my boat is now stalling at 2500 RPM.

Also, I have been asked by a couple of people to check the anti syphon valve which on some boats is attached to the aluminum block at the top of the fuel tank. My 1998 Maristar 200VRS does not have one.

Any other ideas?

So, if you remove the barb fitting that connects the fuel line to the tank and look through it, you don't see a metal ball?

mmthorn
09-11-2011, 08:26 AM
The only barbed fitting on my fuel system is attached to the block near the fuel pump and is for the return line. All other fittings are NPT and flare fittings.

mmthorn
09-15-2011, 08:55 AM
I put a new fuel pump in the boat and the problem is still occurring.

Could a bad ignition system cause the engine to stall/kill at 2800 RPM?

jmhjgh
09-15-2011, 09:59 AM
I am having a similar problem with a 96 PS205. My engine does not stall but surges at 3300 rpm (you can watch the fuel injectors cut-in and out). Does your engine actually kill or will it surge if you leave the throttle on? I have checked similar things but no resolution yet.

JLeuck64
09-15-2011, 10:39 AM
Does your ignition system have a distributor cap and rotor?

Gofast
09-15-2011, 10:52 AM
I had a similar issue with my 95 Maristar. I thought is was a fuel pump went through all the things you have done.

The shop I was using pulled the exhaust hose and found that it had collapsed on the inside ( outside looked nice and new ) which was choking the engine. Replaced both exahust hoses and fixed my problem.

So I would suggest checking your hose, it's free, Just pull the clamps and see if you have any blockage.

My .02 for the really wierd issue your having.

jmhjgh
09-15-2011, 12:36 PM
My PS205 does have cap and rotor. Both visually look good. I will check the exhaust, but something is making the injectors shut down.

jmhjgh
09-15-2011, 04:23 PM
One other thing, I sprayed brake cleaner down the throat when my engine was surging. No change in anything which should rule out a fuel delivery issue.

mmthorn
09-16-2011, 11:14 PM
I am having a similar problem with a 96 PS205. My engine does not stall but surges at 3300 rpm (you can watch the fuel injectors cut-in and out). Does your engine actually kill or will it surge if you leave the throttle on? I have checked similar things but no resolution yet.

Mine does not surge. My engine will kill.

mmthorn
10-17-2011, 11:48 PM
Does your ignition system have a distributor cap and rotor?

I had a similar issue with my 95 Maristar. I thought is was a fuel pump went through all the things you have done.

The shop I was using pulled the exhaust hose and found that it had collapsed on the inside ( outside looked nice and new ) which was choking the engine. Replaced both exahust hoses and fixed my problem.

So I would suggest checking your hose, it's free, Just pull the clamps and see if you have any blockage.

My .02 for the really wierd issue your having.

Well...The prize goes to GOFAST and my dealer. My dealer recommended that I check the muffler and I found that the horizontal baffle within the muffler had collapsed resulting in closed off exhaust openings. The new muffler has a new internal design (less susceptable to collapsing?) visible from the exhaust opening and everything is working fine now.

Thanks for all the help with diagnosing this problem everyone.

FrankSchwab
10-17-2011, 11:56 PM
Thanks for posting your fix. Those of us who may have the issue in the future appreciate it.

/frank

mikeg205
10-18-2011, 12:36 AM
outstanding thread...something to keep in the back your mind..whe tooling around the lake...or river...thanks MM

Gofast
10-18-2011, 03:01 PM
Glad you got it fixed. It sounded to similar and I chased my problem for a few months.

Happy boating!

JLeuck64
10-18-2011, 03:35 PM
Yes! Thanks for posting the fix. Seen way too many of these threads fall by the wayside without resolution...

I have run into plugged exhausts and the runability issues that result with autos before. Never with a boat yet, fascinating!

jmhjgh
10-18-2011, 05:30 PM
I am glad your boat is fixed. My 96 still has the surging at 3300 rpm, and I ended up winterizing it and putting it away. I will check that exhaust hoses in the spring and really hope that I have the same problem as Gofast since I do not have the muffler like your Maristar. Mine still seems electrical the way is surges only at 3300 rpm, but I am hoping this is the fix. Thanks for posting your solution.

tlsbarefoot
10-18-2011, 08:50 PM
I once had a problem with an oil sending sensor that caused a similar issue on a 1995 Correct Craft with a PCM EFI engine.

jmhjgh
10-19-2011, 11:32 AM
What were your symptoms on the 95 CC? What is the theory on how the oil sending unit can cause surging? Thanks