Expert Honda help requested.

[Skinnywater]

I've been chasing this gremlin around for a while.

The engine is a 2007 BF90d with a jetpump.

The symptoms are when cruising at or above 4800 rpm for 10-15 minutes the motor starts a minor surge. Soon after the surge intensifys to a very rythmic surge that can be as abrupt as 1000 rpm. It never dies or quits and when I throttle back it clears up. If I immediately throttle back to idle it idles very smooth.
If I pump the bulb it somewhat clears up.
Sometimes if I shut down the problem will clear up for another 10-15 minutes.
Sometimes I can go for days without a problem.
I think it's starving for fuel and my instinct says it's a low pressure problem.

This is what I've done.
All harnesses have been checked for tightness.
The fuel tank vent is clear. I've removed the fuel tank supply tube checked the screen and tube and visually inspected the tank internals. There was about 12ft. of 3/8 rubber fuel hose that I replaced with 3/8 copper tube and new hose at the ends. The spin on fuel/water seperator is new. The primer bulb is new and all have been triple checked for kinks or obstructions.
Fuel flows freely throught the Honda seperator, through the Honda filter to the low pressure pump.
At idle the low pressure pump shows 5-6lbs with a guage inline. At 5000 RPM it shows 3-4 lbs.
At idle and checking low pressure volume at the inlet of the vapor seperator is......16 fluid ounces in 40 seconds...... I'm suspect here.
My experience on automobiles tells me this fuel pump volume is lacking quite a bit. But then it is a small pump.

If I pump the primer bulb while checking volume at idle, the volume is increased dramatically.

Note that there aren't any buzzers and warnings and no check engine light.
It isn't the rev limiter or engine protection system. It is virtually flawless except the surge.

 

[zzzzz]

Re: Expert Honda help requested.

I checked Hondas' dealer website for any bulletins that might be relevant...nothin' there...the only thing I can think of is to isolate the boat and motor by using a 6 gallon fuel tank and run the boat to see if it acts up on the portable tank...it'll narrow down your quest

 

[Skinnywater]

Re: Expert Honda help requested.

I checked Hondas' dealer website for any bulletins that might be relevant...nothin' there...the only thing I can think of is to isolate the boat and motor by using a 6 gallon fuel tank and run the boat to see if it acts up on the portable tank...it'll narrow down your quest

Thanks z5, your bulletin search was what I was looking for or known common faults.

I'm pretty confident the boats fuel supply is good. I've combed over it suspecting it as being the problem.

My next action is to do a high pressure test. If pressure falls when the problem occurs then I will suspect the high pressure pump is scavenging. Then I'll be back at the low pressure pump.

If the problem occurs and a drop in high pressure isn't seen then I'll be on to a TPS......

 

[zzzzz]

Re: Expert Honda help requested.

AHHH ! you have one of the first batch of injected 90's...make sure that none of the lines going to/from the fuel pressure regulator are pinched/kinked

 

[Skinnywater]

Re: Expert Honda help requested.

AHHH ! you have one of the first batch of injected 90's...make sure that none of the lines going to/from the fuel pressure regulator are pinched/kinked

Yeah, had to wait for it and it isn't a factory jet since they aren't available yet.

All the hoses are perfectly routed.
The problem is far to intermittent to even consider taking it back to the dealer at this time.
Especially with it being his busy time and is prolly booked 2 months out.
Salmon are just starting to stack up in the river, so I'll be diagnosing it myself.

I'll be coming up an adapter for my high pressure guage to work on the Honda by the weekend
I'll post what I find.

 

[Skinnywater]

Re: Expert Honda help requested.

I thought that I might as well mount a permanent fuel pressure (high pressure) guage.

I'm coming up with a permanent 90 deg. fitting at the service check port, a 5 inch section of SS braided fuel hose a SS bracket that will mount at the idle air valve bolts. This guage will mount solid to that bracket, tucked in center of the idle air valve.

http://www.marshallinstruments.com/products/M.cfm

 

[Skinnywater]

Re: Expert Honda help requested.

I ordered a very nice guage to mount permanently in the high pressure circuit.
My plans are to use a banjo fitting at the service check port and use SS tube and fabricate a bracket to plumb it in to look factory.

I usually obsess about custom projects and unsolved mechanical problems.
Sometimes this obsession often has me sitting up in bed in the middle of the night with answers.

This motor was a repower from a previous BF50 that did an awesome job.
The BF90 was the answer to have ample power to pysically load my boat with with more fishing gear, bells and whistles and the added fun factor.

This motor has allowed me to do that for sure, both in my expectations and comparison. And as you might imagine the difference between 50hp and 90 should be substantial.

However, it came to me through the very obvious intermittent surgeing that there are additional elements to this that weren't even seen as a problem since overall performance isn't an issue.

Hmmmm, I've never seen this motor go over 5200rpm WOT, yet VTEC doesn't come into play until over 5200RPM. Ninety HP isn't achieved until 5600 RPM and the motor is capable of 6200 rpm.....hmmmm.

Is the jetpump causing the motor to "run out" before max RPM much the same way as if it were mis-propped?....I didn't think so since a prop is harder to twist then an impeller.
A trip to the river and a quick trimmed up to cavitation (nice rooster tail!)WOT burn-out said NO......5200RPM is all.......hmmmm.

Page 5-45 of my trusty shop manuel has me testing pin1(SG2)and pin2(TH) of the throttle position switch (TP) at idle position and at WOT, the range is to be 0-6000 ohm.

My actual spec's are at idle position it is 650 ohm and incrementally rises to 1900 ohm at approx 3/4 throttle, immediately after it drops to "0" (as in open circuit)for the entire travel to WOT........hmmmm......no check engine light......
Anyone care to give me actual WOT specs? Is it open or should it be like I'm thinking, close to 6k ohm...

 

[FishyFun]

Re: Expert Honda help requested.

The copper supply may be flacking off ever so slightly and clogging things up for you. I would go with a good grade of supply hose 1/2 id. Clamp it as straight as possible with generous sweeping curves if you can.

My nickles worth,
Lee

 

[Frank Martin]

Re: Expert Honda help requested.

wow sounds like you are into this one
first and fore most you need to keep it simple

try a portable 6 gallon tank , my first gut feeling is tha you have a air leek some where in your suply system , this can be confirmed or dispoved by the addition of some clear tigon tubing in the suply line to the VOPOR SEPERATOR that contains the high presure pump . these systems will surge with the slightest amont of air bubels in the high presure side of the fuel system thats why they spend all the extra money putting the elaborate vapor seperator/fuel cooler on the motors , the vapor seperator can only take so much air out of the system ,
a tps or throttle position sensor when checked with a ohm meter MUST be CALIBRATED OR ADJUSTED READING FOR COMPONENT TEMPERATURE
best and easyest to check these components with a dds (honda hand held comuter) they have had a bunch of units leave the factory with a trottle cables out of adjustment , with the dds the throttle cable must push the tps to at least 96% to optain full potential of the motor spec reads 96%+ seldom will go to 100% but this is suposed to be checed by the selling dealer as part of the pre delivery check
motor should see 6000 rpms on a jet pump if it dont you have the wrong impeller in the pump but first motor has to be eliminated as cause

I am a honda dealer and love this new motor but its still a motor like my dad used to say
"if it has a skirt on it or wheels, its going to give you some poblems once and a while" actually thats not exactly what he said had to clean it up a little LOL



good luck

 

[Skinnywater]

Re: Expert Honda help requested.

wow sounds like you are into this one
first and fore most you need to keep it simple

try a portable 6 gallon tank , my first gut feeling is tha you have a air leek some where in your suply system , this can be confirmed or dispoved by the addition of some clear tigon tubing in the suply line to the VOPOR SEPERATOR that contains the high presure pump . these systems will surge with the slightest amont of air bubels in the high presure side of the fuel system thats why they spend all the extra money putting the elaborate vapor seperator/fuel cooler on the motors , the vapor seperator can only take so much air out of the system ,
a tps or throttle position sensor when checked with a ohm meter MUST be CALIBRATED OR ADJUSTED READING FOR COMPONENT TEMPERATURE
best and easyest to check these components with a dds (honda hand held comuter) they have had a bunch of units leave the factory with a trottle cables out of adjustment , with the dds the throttle cable must push the tps to at least 96% to optain full potential of the motor spec reads 96%+ seldom will go to 100% but this is suposed to be checed by the selling dealer as part of the pre delivery check
motor should see 6000 rpms on a jet pump if it dont you have the wrong impeller in the pump but first motor has to be eliminated as cause

I am a honda dealer and love this new motor but its still a motor like my dad used to say
"if it has a skirt on it or wheels, its going to give you some poblems once and a while" actually thats not exactly what he said had to clean it up a little LOL



good luck

Good info Frank and the clear fuel line (tigon tubing)to the seperator is an excellent idea.
This is all , no hurry or worry and is a fun exercise.