| Author | Message | ||
     Dustin Collier Yet to post message Username: directcurrent Post Number: 1 Registered: 01-2025 |
I have a 91 Silver Spur II in my shop right now. The customer had it towed here after getting it back from another shop that tried to fix it and charged him $5000 just for it to brake down on his first drive home from that shop. Now the issues I've been fixing has been long. First there was a missing screw that keeps the ignition switch in place, so it was rotating and not cranking(fixed that). I've discover alot of hacked up wires that I've attempted to wire back up correctly which I'm almost 100% positive I've fixed. This other "shop" wired in a cheap Chinese electric fan thermal relay system in place to turn on the fuel pump as soon as the battery kill switch was turned on with a new wire ran down to the fuel pump, didn't remove the original wire that feeds the fuel pump sending voltage backwards through the system (which I'm hoping didn't damage anything), but I discovered a few relays that didn't work one being the fuel pump relay(fixed now). I can keep going, but I want to get to my issue. The car does start now, but the idle is low, it runs rich, and is hard to accelerate because of the rich condition. Anyone have any advice for me that would be great, and thank you for taking the time to read my post. | ||
| Cliff Biggs Experienced User Username: cliffy Post Number: 161 Registered: 09-2021 |
I had what may be a similar condition that was so rich it spit out black particles from the exhaust stacks on the wall. I cured it by turning the idle air screw and adding air to the idle circuit. It is located right on top of the black throttle housing next to the big round top. There are 3 "screws" (should be silver in color) on it and the middle one ha a slot in it for a screwdriver to add air to the idle circuit. Mine now idles fine and accelerates as it should. I am of course presuming Bosch fuel injection is installed. | ||
| Dustin Collier New User Username: directcurrent Post Number: 2 Registered: 01-2025 |
Cliff what I'm finding and reading on this Bosch jetronic system is the idle air flow is electronically controlled and is set from factory with not adjustment. I did just find out the fuel metering body isn't putting proper flow out to the fuel injectors causing a misfire from cylinder 1 and possibly 3. The other issues I have is I can't check codes because the gauge cluster isn't working and the customer doesn't want to spend $1600 on a used cluster that might not work. Flying blind isn't fun. However, at this point I believe pulling fuel injectors and testing them for flow and spray pattern is my next logical step . Any other advice is appreciated. | ||
| Jeff Martin Frequent User Username: jeff_r_1 Post Number: 714 Registered: 07-2018 |
I don't pretend to know about these systems, but I've come across many posts about them with these problems. The car is 34 years old and I doubt the fuel distribution system has never been serviced (rebuilt). Then there are other things like worn and dirty injectors, is the fuel pump putting out the pressure it should, fuel filters in the system _ debris in the fuel tank, on and on ? Have a look at this. https://www.youtube.com/watch?v=O07KlxiUbDY It's gone for 34 years with out anything going wrong with the fuel delivery system (assuming), spending 2,000.00 or more is to be expected. That's actually a bargain when you consider the new Rolls Royce's by BMW, and the hefty bills that come about as they begin to age. Show this to you customer: https://www.youtube.com/watch?v=NKzGfaoDWNk&t=2699s | ||
| Cliff Biggs Experienced User Username: cliffy Post Number: 162 Registered: 09-2021 |
Mine is a Jetronic w/ Lambda Its idle mixture is set at the factory but the idle rpm can be adjusted with the air bleed screw. That was my issue. Someone had closed it down to the max low rpm (jammed the screw slightly at its bottom) and that caused the very rich idle and poor running. Once I raised the rpm using the bypass air screw all was normal. Are you sure you do not have a bypass air screw on the top of the inlet next to the large round cover? | ||
| Darryl Watson Frequent User Username: inox Post Number: 214 Registered: 04-2015 |
Re Jeff's link above I had the fuel metering head rebuild on our 1990 SZ a number of years ago. The rubber seal(s) and other bits of magic wear out. I bought a Merc kit but it didn't fit. The mixture adjustment screw is hyper critical and it takes a few seconds to stabilise after adjustment. I ended up having it adjusted by a RR Bentley specialist not far from me. | ||
| Dustin Collier New User Username: directcurrent Post Number: 3 Registered: 01-2025 |
hopefully this picture attaches. I've tested fuel pressure and its was 6.2 bar upper and 5.8 lower. Should I be looking somewhere else for the bypass air screw?  | ||
| Dustin Collier New User Username: directcurrent Post Number: 4 Registered: 01-2025 |
the picture I posted is where on the previous models was able to be adjusted right next to the fuel manifold. | ||
| michael vass Frequent User Username: mikebentleyturbo2 Post Number: 816 Registered: 07-2015 |
Are you sure the ecu is being told the engine is cold? | ||
| Dustin Collier New User Username: directcurrent Post Number: 5 Registered: 01-2025 |
That's the issue I'm wondering as well. The coolant temp sensor ohmed out just fine. I did replace the throttle position sensor because of corrosion and not reading correctly. Unfortunately I can't hook up my Snap-On Zeus to see readings. I have tested the coolant temp vs ohm reading at the temp sensor. I can't find a bypass air screw on this system anywhere. I'll have to find a better way to post pictures because it keeps telling me they are to big. | ||
| David Gore Moderator Username: david_gore Post Number: 4291 Registered: 04-2003 |
Dustin, What are your image size and resolution details? I use 300dpi resolution and 800px x 800px as maximum image size for forum posting. Our Administrator has advised me when I raised this problem in the past that the limitations of the original forum software due to its age and the issues/difficulties that would be involved in transferring the existing post files to later forum software effectively preclude transfering the existing forum archives to currently available forum software. | ||
| Jeff Martin Frequent User Username: jeff_r_1 Post Number: 715 Registered: 07-2018 |
I use this free program, paint.net to resize the photos down to 800 x 800, or smaller. https://www.dotpdn.com/downloads/pdn.html Here's a screen shot of a photo that's too big at 660 x 939, so you reduce it to 800 x 562. Change the largest number to 800, and the program will do the rest, as long as it's smaller then 800 x 800, it will post here. Click on "Image" and then "resize". There's probably an easier way of doing it, but that's what I do.  And the photo:   | ||
| michael vass Frequent User Username: mikebentleyturbo2 Post Number: 817 Registered: 07-2015 |
Hi Dustin Just checking you have the correct sensor, one should be black and one brown. there are a lot of incorrect part number listings for these two, as indicated by the loom plug colour. I found out the hard way lol Good luck Mike | ||
| Dustin Collier New User Username: directcurrent Post Number: 6 Registered: 01-2025 |
Michael the temp sensor I ohmed out is down behind the air pump which according it diagrams that should be the coolant temp sensor. |
