1985 LTD Loss of Power

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Been a while since I updated this thread. Have had a power issue with the '85 LTD and took it off the road and into the garage in early July. Thankfully I have my 1800 to ride as well.

One of the troubleshooting issues is that there are no error codes on the ECU that makes identification of the issue that much more difficult. I do prefer fuel injection over carbs, but this is befuddling me.

I replaced the fuel pump and injectors as I mentioned earlier and possibly in another thread. The fuel pump was an Airtex E8312 - an in tank pump. When I started to have power issues again, I thought this might be the problem. I replaced it with a Spectra SP1186 - external fuel pump. This did not fix the problem, but the banjo bolt fitting is better for the application.

I have checked the fuel pressure in the system, 38 PSI with key on, 36 PSI with the engine at idle. Tested the fuel pressure up to 4000 RPM - steady at 36 PSI. No issues with the fuel delivery or the fuel pressure regulator.

I went back to Ontario in July and took the PB (MAP sensors), Gr/Gl (camshaft sensor for injector timing), and TPS off the bike I have there. When I got back, I replaced each sensor one at a time to determine the issue, but again no joy. The only sensor I left in place was the TPS.

I did not do the Ns (crankshaft sensor for engine timing) because I would have to take the front off the bike. I did do the continuity and resistance checks and found this sensor to be out of spec. I replaced it with a new PG sensor harness for an '85 ASPY/Interstate. The engine blocks are the same so I was able to install the sensors over/under the crankshaft wheel. The mounting arrangement is such that the air gap is predetermined and within spec. Here is the PG sensors installed:
New Ns Sensors Installed 2.jpg


I will only be using one of the sensors as the Ns sensor, and have the other as a spare so that if I need it I can just change the connector under the shelter and will not have to take off the front of the bike. Having done this, I have not fixed the issue.

I found a thread over on the CX500-650 forum about the PB sensor. Here is the thread:https://cx500forum.com/forum/cx500-cx650-turbo-forum/17499-pb-sensor-replacement-11.html.

The information is excellent and pertinent to what I am experiencing. The Reader's Digest version is that the PB sensor affects the operation of the engine up to 3000 RPM. After which it is no longer in play. I tested this and found that up to 3000 RPM, there is an increase in manifold vacuum of 10 to 12 inches. After 3000 RPM there is no increase in manifold vacuum so the PB sensors are maxed out and as I mentioned, no longer in play.

The fellows over on the CX forum have sourced a replacement MAP sensor and it is a:

Brand: Denso.
Type number: 100798-5630. Suzuki orderingnumber: 15620-35F00.
Suzuki description: Sensor Boost, IAP (Inlet Air Pressure) sensor.

They have found it to be an almost exact replacement sensor and many have installed this sensor to rectify the issue that I am experiencing. When I read this I sourced two and purchased them. One of the fellows took a faulty OEM PB sensor apart and found the internal connections to be less than stellar and problematic. It was also mentioned that the difference in technology between the modern MAP sensor and older ones is significant.

Here are some pictures of the sensor and my mods to the connector(s):
Suzuki MAP Sensor 2.jpg
New PB Sensor Pigtails.jpg
pb sensor schematic.JPG
PB Sensor Mod 4.jpg



Since I have tried, within reason, everything else, I am going to install the Suzuki MAP sensors tomorrow and hopefully will see a significant improvement such that the issue I am having is fixed.

A lot of issues in play with a fuel injected bike. Learning a lot and will be able to update one of my other threads with a synopsis of what I now know about the '85 LTD Fuel injection system.

More to follow - good news I hope.
 
Think it's a bit of a crap shoot, but something has to give. Lots of information on the various forums; however, it's sometimes hit and miss. Even in the supplement troubleshooting guide it has specifics, but when you address these and no joy, it lists a host of other potential possibilities such as every other sensor.

Searching for this issue reminds me of the '04 Jeep Liberty I had. The speedometer stopped working so I took it to the local Jeep dealer to be fixed. They did every recall that had been issued, replaced the black box as well, but never did find the fault. Talked to the engineers in Detroit as well.

Had another small issue with the Jeep and the fellow who was doing the fix had to check about 8 things before getting to the issue, even though he knew exactly what to do and where to go. Asked why and he mentioned that if he did not go through the check list and he was wrong, he would be on the hook for the work, understand his predicament.

Would not like to have my 1800 have an issue like this. The shop would have a field day.

Cheeers
 
I'll give you credit for sticking with it. I truly feel your pain with no help from a OBDII or anything like that. I've been keeping an '83 Westfalia puttering around the southwest (and even further sometimes) for the last ten years. Digijet fuel injection with various sensors (including a "flapper" that serves as the MAF sensor). When something goes off kilter, you gotta isolate the bad actor the hairy chested man's way. No help from CIL or code scans.

Sounds like you're all over it! Also sounds like these carb racks ain't so bad after all... :BigGrin:
 
Changed the PB sensors. It does idle better and when at speed runs like a top. Still has a miss, not a stumble this time, but a miss.

I did change the vacuum hose to the sensors but it is slightly larger in diameter than I want. Will get a smaller diameter size vacuum hose.

I may have to backtrack a bit and check the coils and wires as well. Replaced these items end April/May time frame, who knows.

Sensors and coils generally do not do well when hot. If it were the coils, I would expect the bike to shut down, cool down, then start again. Possibly one of the other sensors is bad. The troubleshooting guide also mentions the ECU - may have to have my brother take the one off the bike in Ontario and send to me.

I have a theory that I am higher in the food chain than this bike, maybe not at this time, but I will solve this. Man does not like a mystery.

As for carbs, while I would like to take a 12 gauge to this bike at this time (if I had one), I would still go for fuel injection over carbs.

A mystery for sure, but one that will be solved.

Cheers
 
Have you checked for air leaks? I'm not sure how they affect an injection system but I'm sure there is an effect. Be sure the vacuum lines you use are as stiff walled as possible and do not leave much if any extra length. They can act as dampeners and deliver lower vacuum than they should.
 
Resistor caps on ignition wires can deteriorate causing intermittent miss. You can check by measuring resistance from cap to cap for each coil. You should get the same resistance for each coil of 20 to 25k ohms. If you get infinity on a coil then you have found your miss.

It is a long shot but easy to check.
 
Okay - hopefully last installment. Went back and reassessed the situation. Remember my Father telling me years ago when I drove a '65 Plymouth Fury and had just done a tune-up, and the car would not start especially after I had drove it to where I did the work. After a few hours of turmoil, phoned Dad and he told me to go back to the beginning.

I thought about my bike and the only item(s) that I had changed that would affect spark were the coils. I took the new coils off and checked them against the original coils, and one coil resistance when cold was less than spec. This would indicate to me that when hot the coil resistance would probably be less. Installed the original coils and wires and to my pleasant surprise the engine runs well. No miss at low RPM. played around in some traffic circles and it never missed a beat. Now to give it a good ride to clean out the cob webs that surely accumulated over the last 2 months.

This has not been without a silver lining. Found the Ns (crankshaft) sensor to be out of spec - resistance reducing, good time to replace. The TPS was also out of spec. The new to this bike TPS is in spec so again a good change. Cleaned up the timing belt covers, looks much better.

Installed the Suzuki MAP sensors in place of the original PB sensors and these worked well. Good source of a PB replacement if needed. Have since put the original PB sensors back in.

Found out that the original vacuum lines are a different size than what can be taken off the shelf. Replaced a couple of small lengths but had to take the fitting in with me to try the different size hose.

Got to check the fuel system pressure with key on and at idle. Something I wanted to check for a long time. 38 PSI with the key on and 36 PSI at idle.

Another item on my to do list was compression. Checked yesterday, 125 PSI across the board - can live with this.

Balanced the cylinder banks once I had the bike straightened out. Because it is fuel injected, cannot balance cylinders 1-3, or 2-4, only left-right bank. Here is a picture of the balance:
Engine Balance.jpg


It was nice riding the 1800 again. Went for a ride down the coast to Port Renfrew for a burger (100 Kms) and Sonya mentioned that the 1800 was a nice bike but she preferred the 1200. Doing something right with the 1200.

Lastly, I learned a lot about the FI system.

Now to wait for the next challenge.

Cheers
 
I also checked the plug caps and the resistors in them. All was well. Have sourced a parts place that has 7 mm wire so I can renew the existing ones that are not quite supple.

Have to update my maintenance spreadsheet now.

Cheers
 
I have changed out the OEM PB sensors and put the Suzuki boost sensors, IAP (Inlet Air Pressure) in place of. Bike has been running well and have just did the first fill up since these were installed. City/highway driving and the bike is averaging 16.28 Km per litre (38.29 USMPG or 45.98 IMPG). Pretty much in line with what I was getting before with the OEM PB sensors. Going to leave these in for the time being. A road trip would really decide the efficiency and benefit.

Cheers
 

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