reeltimejim
Recruit
- Joined
- Aug 21, 2015
- Messages
- 2
Reaching our to anyone that has any suggestions, I've tried about everything and running out of options. This is a rather long post but I think will answer most questions anyone would have about the problem and what I've checked.
To begin, I had an earlier fuel problem last year, turns out the ECU had a bad MAP sensor it was running rich, bought a new Brucato ECU. Also had the injectors serviced, new electric pump, new regulator, new VST float and needle, gasket, etc. Everything worked great for about a month after that, quick hole shot and about 5700 RPM top end all trimmed out. All good so I thought.
A few weeks ago I noticed it was down on top end power and and RPM, and the problem gradually became worse, first it wouldn't push over 4500 RPM, then eventually where it would bog down under load and unable to get on plane or reach over 2500-3000 RPM. It appears it is still a rich condition I am fighting here, plugs were soaked and a lot of oil in the induction plenum. I've been through a number of tests which I'll describe below, and was hoping someone might be able to clue me in on some other things to check.
First, I checked compression again on all holes - 130 psi for all six with no variations, although I did not do a leak down test yet. It looks like everything with the ignition system and timing is fine. The stator, trigger, switch boxes are all new from CDI and checked out with all of the static and running tests for voltage and resistance. Flywheel is in good shape, all magnets are secured. Coils are not new but checked out OK on the resistance tests and getting good primary voltage. Also new wires and plugs BR8HS-10. All the spark gap tests showed 1/2 inch strong blue spark on all cylinders.
When I pull plug wires under load, it seems I am only getting a noticeable RPM change on the top two cylinders (1 & 2) on each bank, all the lower cylinders appear dead with indistinguishable or no change in RPM. To start it I have to open the throttle up a bit, and the tach seems to jump around a lot at low RPM when I do get it to idle. After about 30 seconds when the motor begins to warm up, the RPMs increase significantly, as I'm assuming the ECU leans out the fuel when the temp sensor reading is over 90 deg C, this also leads me to believe it is running too rich.
The timing appears to be in spec for the cranking tests, 4-6 deg ATDC for idle timing and max timing at 22 deg BTDC. Also timing is 4 deg ATDC when running at idle. When I remove the white/black bias wire from the detonation controller the max timing lowers to about 16 BTDC, but has no effect on idle timing. This is actually the opposite of that the manual says should happen, so I removed the idle stabilizer and detonation modules, jumped the bias terminals on the switch boxes and no change there. Not sure if the detonation controller is working properly, the sensor tests ok, but the controller voltage to the ECU is a constant 0.66 volts, regardless of load or RPM. Seems this may not be working properly, but not sure if this is the major problem. Bias voltage to switch boxes is within specs with both idle and detonation boxes connected.
Voltage regulators are also new from CDI, and getting the proper voltage and current there. Also recently replaced the water pump, t-stats, poppet and temperature sensor, I was getting erratic temperature gauge readings and the new sensor fixed that. However, the old temperature sensor wires to the ECU were reading the correct resistance vs. temperature, just the sensor resistance on the gauge wire was off specs.
So onto the fuel side, I've got fresh fuel, new anti-siphon valve, new fuel lines, new primer bulb and new filters. Pulse pump has been rebuilt, new electric pump, new pressure regulator, serviced injectors and all new seals and gaskets. VST has new needle and float, that appears to work fine. Fuel pressure at key on and at idle 34-36 psi, holds 25 psi for 30 minutes after it is shut off. All screens and final filter at pump and regulator are clear. All three injector circuits read complete with the correct resistance, and the operating voltage to each circuit is within specs when running. I have a scope and can measure the pulse width if that data would tell me something, but I don't know what the pulse width is supposed to be vs. RPM or load.
When I drained the VST, I noticed the fuel was very rich with oil. We compared with another sample mix of 50:1 and added oil until we got to about 5:1 to get the same mix. So obviously I had a problem with the oiling system, either the check valve at the bottom of the VST is letting to much oil in, the pulse valve is not bleeding off remote tank pressure properly, or the pump gear is worn out. The throttle linkage arm is attached and set properly to the oil pump. Also installed all new bleed check valves and Tygon hoses, I can see fuel and oil pumping though those lines. Also air temperature and head temperature sensors are new.
Next, I bypassed the oil system completely (diverted oil pump output back into the reservoir), purged all of the straight fuel, installed new plugs and ran it off a shop tank with 50:1 mix. Still no change in the problem, although I know I am getting the correct mix now. I bought the Mercury block off kit for the oil pump, so I'll probably go ahead and install that eventually. I still want to find what the problem is, I will run the oil pump volume test today.
Having completed most of the factory manual tests and diagnostics, I measured the induction plenum vacuum at idle (where the ECU MAP hose connects), it was only 5 in Hg. This seems real low, I expected to be around 15 in and suspect I may have a major vacuum leak? I suppose this would also trigger the ECU to significantly increase injector pulse widths, which is consistent with what appears to be a rich condition.
So next I blocked off the intake ports and ran a smoke test on the induction plenum, haven't found any leaks yet visible externally, I think I may also have to block off the exhaust to really tell. I suppose the fact that I have little or no combustion in the bottom four cylinders could also be causing the low vacuum, maybe there is no leak at all? Reeds were inspected and all look OK. I also understand exhaust restrictions could cause low vacuum, or the tuner could have become loose, and I will remove the lower unit to check that. I just doesn't seem that could be a problem that developed so quickly. Are there any other tests I can run to help isolate a possible vacuum leak, maybe a crank or case seal problem, or head gaskets? Or could the pulse valve to the oil tank fail in such a way to cause a vacuum leak?
After running about 2 gallons through the motor with the 50:1 shop tank and another new set of plugs, it seems that I can get it to idle a little better running in a water tank, but it's still down on power. Could it be the engine is just so saturated with oil it will take longer than I think to burn off all that extra oil? I still can't get it on plane on the water.
I think the low vacuum might be my major problem here, but not a lot of information out there on what it should be. And I'm not certain the low vacuum is caused by a leak, or another problem. I doubt it is a problem with the new ECU dumping too much fuel, but I suppose it's always a possibility if there is something I can check there. Maybe I should get the software so I can communicate with ECU to look at the data, or send back to Tony to verify it is ok, The harness wiring all checks out and is in good shape. Note the Brucato ECU only uses the MAP, air temp, head temp and coil signals to trigger injectors, the TPS is not used.
I'm an engineer and usually pretty good at sorting these things out, but this one has me chasing my tail. I'm determined to solve this problem even if I have to rebuild the entire engine. Any suggestions on where I go from here would be greatly appreciated,.
Thanks! Jim
To begin, I had an earlier fuel problem last year, turns out the ECU had a bad MAP sensor it was running rich, bought a new Brucato ECU. Also had the injectors serviced, new electric pump, new regulator, new VST float and needle, gasket, etc. Everything worked great for about a month after that, quick hole shot and about 5700 RPM top end all trimmed out. All good so I thought.
A few weeks ago I noticed it was down on top end power and and RPM, and the problem gradually became worse, first it wouldn't push over 4500 RPM, then eventually where it would bog down under load and unable to get on plane or reach over 2500-3000 RPM. It appears it is still a rich condition I am fighting here, plugs were soaked and a lot of oil in the induction plenum. I've been through a number of tests which I'll describe below, and was hoping someone might be able to clue me in on some other things to check.
First, I checked compression again on all holes - 130 psi for all six with no variations, although I did not do a leak down test yet. It looks like everything with the ignition system and timing is fine. The stator, trigger, switch boxes are all new from CDI and checked out with all of the static and running tests for voltage and resistance. Flywheel is in good shape, all magnets are secured. Coils are not new but checked out OK on the resistance tests and getting good primary voltage. Also new wires and plugs BR8HS-10. All the spark gap tests showed 1/2 inch strong blue spark on all cylinders.
When I pull plug wires under load, it seems I am only getting a noticeable RPM change on the top two cylinders (1 & 2) on each bank, all the lower cylinders appear dead with indistinguishable or no change in RPM. To start it I have to open the throttle up a bit, and the tach seems to jump around a lot at low RPM when I do get it to idle. After about 30 seconds when the motor begins to warm up, the RPMs increase significantly, as I'm assuming the ECU leans out the fuel when the temp sensor reading is over 90 deg C, this also leads me to believe it is running too rich.
The timing appears to be in spec for the cranking tests, 4-6 deg ATDC for idle timing and max timing at 22 deg BTDC. Also timing is 4 deg ATDC when running at idle. When I remove the white/black bias wire from the detonation controller the max timing lowers to about 16 BTDC, but has no effect on idle timing. This is actually the opposite of that the manual says should happen, so I removed the idle stabilizer and detonation modules, jumped the bias terminals on the switch boxes and no change there. Not sure if the detonation controller is working properly, the sensor tests ok, but the controller voltage to the ECU is a constant 0.66 volts, regardless of load or RPM. Seems this may not be working properly, but not sure if this is the major problem. Bias voltage to switch boxes is within specs with both idle and detonation boxes connected.
Voltage regulators are also new from CDI, and getting the proper voltage and current there. Also recently replaced the water pump, t-stats, poppet and temperature sensor, I was getting erratic temperature gauge readings and the new sensor fixed that. However, the old temperature sensor wires to the ECU were reading the correct resistance vs. temperature, just the sensor resistance on the gauge wire was off specs.
So onto the fuel side, I've got fresh fuel, new anti-siphon valve, new fuel lines, new primer bulb and new filters. Pulse pump has been rebuilt, new electric pump, new pressure regulator, serviced injectors and all new seals and gaskets. VST has new needle and float, that appears to work fine. Fuel pressure at key on and at idle 34-36 psi, holds 25 psi for 30 minutes after it is shut off. All screens and final filter at pump and regulator are clear. All three injector circuits read complete with the correct resistance, and the operating voltage to each circuit is within specs when running. I have a scope and can measure the pulse width if that data would tell me something, but I don't know what the pulse width is supposed to be vs. RPM or load.
When I drained the VST, I noticed the fuel was very rich with oil. We compared with another sample mix of 50:1 and added oil until we got to about 5:1 to get the same mix. So obviously I had a problem with the oiling system, either the check valve at the bottom of the VST is letting to much oil in, the pulse valve is not bleeding off remote tank pressure properly, or the pump gear is worn out. The throttle linkage arm is attached and set properly to the oil pump. Also installed all new bleed check valves and Tygon hoses, I can see fuel and oil pumping though those lines. Also air temperature and head temperature sensors are new.
Next, I bypassed the oil system completely (diverted oil pump output back into the reservoir), purged all of the straight fuel, installed new plugs and ran it off a shop tank with 50:1 mix. Still no change in the problem, although I know I am getting the correct mix now. I bought the Mercury block off kit for the oil pump, so I'll probably go ahead and install that eventually. I still want to find what the problem is, I will run the oil pump volume test today.
Having completed most of the factory manual tests and diagnostics, I measured the induction plenum vacuum at idle (where the ECU MAP hose connects), it was only 5 in Hg. This seems real low, I expected to be around 15 in and suspect I may have a major vacuum leak? I suppose this would also trigger the ECU to significantly increase injector pulse widths, which is consistent with what appears to be a rich condition.
So next I blocked off the intake ports and ran a smoke test on the induction plenum, haven't found any leaks yet visible externally, I think I may also have to block off the exhaust to really tell. I suppose the fact that I have little or no combustion in the bottom four cylinders could also be causing the low vacuum, maybe there is no leak at all? Reeds were inspected and all look OK. I also understand exhaust restrictions could cause low vacuum, or the tuner could have become loose, and I will remove the lower unit to check that. I just doesn't seem that could be a problem that developed so quickly. Are there any other tests I can run to help isolate a possible vacuum leak, maybe a crank or case seal problem, or head gaskets? Or could the pulse valve to the oil tank fail in such a way to cause a vacuum leak?
After running about 2 gallons through the motor with the 50:1 shop tank and another new set of plugs, it seems that I can get it to idle a little better running in a water tank, but it's still down on power. Could it be the engine is just so saturated with oil it will take longer than I think to burn off all that extra oil? I still can't get it on plane on the water.
I think the low vacuum might be my major problem here, but not a lot of information out there on what it should be. And I'm not certain the low vacuum is caused by a leak, or another problem. I doubt it is a problem with the new ECU dumping too much fuel, but I suppose it's always a possibility if there is something I can check there. Maybe I should get the software so I can communicate with ECU to look at the data, or send back to Tony to verify it is ok, The harness wiring all checks out and is in good shape. Note the Brucato ECU only uses the MAP, air temp, head temp and coil signals to trigger injectors, the TPS is not used.
I'm an engineer and usually pretty good at sorting these things out, but this one has me chasing my tail. I'm determined to solve this problem even if I have to rebuild the entire engine. Any suggestions on where I go from here would be greatly appreciated,.
Thanks! Jim
