5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

[jkel1124]

OK I would really appreciate some help here. I've got a 2000 Seaswirl 195 Volvo Penta 5.0 GI PEFS that was converted to a 5.7 last year after I purchased it (previous owner failed to winterize it). It has 150 total hours on it, and only approximately 15hrs on the new motor. The fuel pump assembly ($750) was replaced along with the motor last year. Well the boat ran perfect for the first month or so, but has been going down hill. It started hesitating under a load (cutting out and popping from the TBI) so I replaced the fuel filter. It still did the same thing so I replaced the injectors in the TBI. That did not help either. It seems to be getting worse. It will start ok and run fine at low rpms but then start sputtering and popping at higher rpm. The thing that really boggles me is, if I just open it all the way up to WOT it will stop cutting out and run perfectly to 5000rpm and continue to run great until I let off the throttle, then back to sputtering. Did a fuel pressure test and high pump tested about 34psi, but the low seemed to be a vacuum (my gauge is kinda stuck at 3psi but when hooked to the low pump it pulls to 0). Because it runs great at WOT it seems that the fuel pump (neither high nor low, because the low only feeds the high) could not be the problem and my gauge must be malfunctioning. Someone please let me know if my theory is correct, and maybe point me into the right direction (my brain is hurting and It's starting to drive me nuts). Thanks in advance!!!!

 

[BreakOutAnotherThousand]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

Test your MAP sensor, and Throttle position sensor.


Check the schrader valve on the low pump, you need to really know your correct fuel pressure.

 

[jkel1124]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

Ok, I will try to test the pressure with a different gauge then. Am I correct in assuming that the problem could not be the fuel pump assembly if it will run fine at WOT? I may also try to test the pressure from an external fuel tank to eliminate a possible blockage in the OEM fuel tank. I will also see what I can do about checking those sensors as well. Thanks for the response and info!

 

[BreakOutAnotherThousand]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

I meant check the schrader valve on the low pressure pump.
I've had 2 fuel cells that the pin on the schrader valve sat too deep, and the pressure gauge did not
depress it enough, resulting in no reading.

 

[jkel1124]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

I meant check the schrader valve on the low pressure pump.
I've had 2 fuel cells that the pin on the schrader valve sat too deep, and the pressure gauge did not
depress it enough, resulting in no reading.

Will do. I'll check it this afternoon and let you know. Thanks!

 

[jkel1124]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

Well the shrader valve was fine so I'm working on getting a new gauge.

 

[jkel1124]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

Well I checked the low pressure side while out on the water with a new gauge...here are the results: 20-22 while at idle. When I open it up it begins bouncing from 10-20. It still runs great at WOT but as soon as I let off a little the popping and cutting out begins. It also runs fine up to 2800 RPM.

 

[BreakOutAnotherThousand]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

This is very similar to my past situation.
However, if you read my thread, I still don't understand what I really did to fix it.


High pressure on the low pump, they will tell you is high, but Ive had 2 new pumps read the same, maybe a new Volvo spec?? I dunno.


Have you checked your timing??

 

[jkel1124]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

This is very similar to my past situation.
However, if you read my thread, I still don't understand what I really did to fix it.


High pressure on the low pump, they will tell you is high, but Ive had 2 new pumps read the same, maybe a new Volvo spec?? I dunno.


Have you checked your timing??

I have not checked my timing. It was set by the shop when the new engine was put in and ran great for a good while. I did check to make sure it was tight. It appeared to be tight so I assumed because it had not moved I could eliminate this as a possible problem. I can check it though to be sure (just a PITA because I will have to remove the rear interior parts). Thanks for the input!

 

[jkel1124]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

So here is the latest. I bit the bullet and installed a new fuel pump assembly. The fuel pressure is now perfectly within specs at 12 on the low pump and 30 on the high. I took it out and lake tested, but nothing changed. I then used an external fuel tank to eliminate the fuel system as a possible problem, but still same thing. Next I checked the timing, and it was right on. I am determined to find this problem! I just don't understand why it will run so well under 3000RPM or wide open throttle. Any other suggestions are greatly appreciated. Thought about maybe replacing the distributor as "Breakoutanotherthousand" did. Thanks again guys!

 

[BreakOutAnotherThousand]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

It still sounds like a reaction to timing.
The ECU will get it's timing information from the MAP sensor, TPS, and coolant sensor.
They should be tested for out of range readings.
Verify you shunted the ALDL connector before setting your timing to 8 degrees before zero, you need a timing light with advance.
Start the engine, shunt the connector, set you timing light to 8 degrees advanced, set the timing to the zero mark.



OMG, I just realized what I did!!! I set my timing light to -8 degrees, not +8, I was 16 degrees off on timing the first time!!!

 

[jkel1124]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

OMG, I just realized what I did!!! I set my timing light to -8 degrees, not +8, I was 16 degrees off on timing the first time!!!

Wow...at least now you know what fixed it. I don't think mine will even run at -8 degrees. I checked the timing just as it showed in the book (shunting the ALDL), and it was right on. I agree, it does sound like a timing issue. I will continue my diagnosing and advise what I find. Thanks again.

 

[Tail_Gunner]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

Well its spark or fuel..One of the great things about tbi..you can watch your injectors deliver fuel...(fun stuff)..

Just put the muff's on run it up to 3000 and watch your injectors if your getting uneven fuel they will show the same pattern your engine is missing at...Thats a old motor have you changed your cap it may be porous or cracked..wires..And again you may need to take contact cleaner and clean all of your FI contacts.

And of course you can take a plug wire put your finger in the plug hole turn it over and see if it hurts...:facepalm:..

 

[jkel1124]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

So just messing arround today I decided to unplug the MAP sensor to see what happens. No popping. Wow! So thought the MAP sensor must be bad. Replaced it and back to same problem. I can feel strong vacuum from the hose. Why will it run fine if unplugged i wonder??? I feel like I may finally be making some progress now that I have some what narrowed down the problem. Now where to go from here?

 

[BreakOutAnotherThousand]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

If unplugged the ECU goes into base timing mode.

Im still inclined to think it's a timing issue.

You should test the MAP sensor first.

NAPA Marine
CRB 21961
or
AC Delco
213-1545
Amazon has then for $36.00

 

[hizel]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

If unplugged the ECU goes into base timing mode.

Im still inclined to think it's a timing issue.

You should test the MAP sensor first.

NAPA Marine
CRB 21961
or
AC Delco
213-1545
Amazon has then for $36.00

Please let me know if the MAP sensor works, this is the exact problem I have on the same engine.

 

[jkel1124]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

The new map sensor did not work. I did, however, enjoy plenty of wakeboarding yesterday with the MAP unplugged and had almost no problems (it seems a little hard to start and maybe a little less power). Ordered a new TPS and will let you know the outcome. If that doesn't do it then it's going to the shop...2 week wait right now .

 

[Tail_Gunner]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

The new map sensor did not work. I did, however, enjoy plenty of wakeboarding yesterday with the MAP unplugged and had almost no problems (it seems a little hard to start and maybe a little less power). Ordered a new TPS and will let you know the outcome. If that doesn't do it then it's going to the shop...2 week wait right now .

I was not kidding when i mentioned watching the tbi injectors spraying at all rpm level's . The fact that your engine runs with out a map sensor is not good. Maybe a ecu

 

[BreakOutAnotherThousand]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

I was not kidding when i mentioned watching the tbi injectors spraying at all rpm level's . The fact that your engine runs with out a map sensor is not good. Maybe a ecu

Not true, the ECU goes into default timing mode for the MAP sensor, the other sensors still send information to the ECU.

If he runs great at WOT, I would rule out injectors.

 

[Tail_Gunner]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

Not true, the ECU goes into default timing mode for the MAP sensor, the other sensors still send information to the ECU.

If he runs great at WOT, I would rule out injectors.

http://www.pirate4x4.com/tech/billavista/MEFI/

Here's a basic look at how the sensors in the speed-density MEFI-4 fuel injection work.

Engine load is primarily determined by sensing the current engine speed and reading the manifold pressure via the manifold absolute pressure (MAP) sensor (this is similar to old-fashioned vacuum signal). The MEFI module uses RPM and MAP to select data from a table with rows and columns of numbers that represent injector pulse width values (milliseconds of on-time). When the ECM needs to know how much fuel to deliver it reads the MAP and RPM, then it refers to the corresponding row and column in its fuel table to obtain the correct injector pulse width, also known as the “base pulse width”. Once this pulse width value is obtained there are adjustments made to it based upon other engine operating conditions, however MAP and RPM are the main factors involved in selecting the base value.

The engine’s spark advance is also selected in similar fashion. Again, there is a table in the ECM ’s memory with rows and columns of numbers that specify degrees of advance. The desired advance value is chosen based upon RPM and MAP. Once the desired spark advance is obtained, other operating conditions are evaluated and used to adjust the value.

Again a great thing with tbi you can watch the injector pulse rate..use a neon light to illuminate them and thing's become very clear. No map sensor and the ecu cannot go to the correct table..yes it could run a default map but why...