| Author | Message | ||
     JSeamanGUEST Unregistered guest Posted From: 92.40.241.136 |
Forgive this being in the wrong place, I have been waiting for days to get my registration approved and just realised I can post here as a guest. I have a 1991 Bentley Eight which is causing me trouble. I have only had the car for a week and can't find any manuals etc so I'm in need of some tech support. I was driving it when the Check Engine warning light came on and it seemed to enter a limp home mode. This cleared when I stopped at a junction but happened a couple more times on my journey (about 10 miles). I then stopped the car and when I went to restart it a few minutes later it would turn but not fire. I have no spark, both rotor arms spin, there is voltage at the coils and I have fitted a new CPS which has made no difference. Battery is good and the ECU doesn't show any sign of water ingress. I have also tried grounding the engine/chassis with a jump lead as I was told there are issues with the ground quality on this year of car. If anybody has any help they can offer regarding fault finding I would love to hear it. James VIN SCBZE00A8MCH3512 Welcome James - have relocated your post into the appropriate location. Suggest you browse the Technical Library and download information relevant to your vehicle: http://rrtechnical.info/ David (Message approved by david_gore) | ||
| JSeamanGUEST Unregistered guest Posted From: 92.40.241.136 |
David, Thank you for posting this up for me - I couldn't find any workshop manuals etc that would help for a 1991 Bentley Eight - I had been looking for a while so was hoping for some tech input on fault finding James PS What do you have to do to get approved to post on here?! (Message approved by david_gore) | ||
| David Gore Moderator Username: david_gore Post Number: 1161 Registered: 4-2003 |
Hi James, You do not have to be a Club member to join this Forum, we welcome anyone from anywhere in the world who has an interest in Rolls-Royce and/or Bentley motor vehicles. All you need to do is register using the "Register" button in the top right hand corner of the page and your membership is usually confirmed within a day or two. The post-1990 section of the Technical Library is a work-in-progress however there is a considerable amount of documentation available for these vehicles already. The following link shows what is currently available and there is no charge for downloading what is available: http://rrtechnical.info/sz/sz30k.htm | ||
| JSeamanGUEST Unregistered guest Posted From: 92.40.241.136 |
David, I did try and register a week ago and never got a response until last night which rejected me. I assume it is because I forgot my surname but it didn't tell me? I registered again last night but am still awaiting approval. Thanks for the link but there isn't too much information about values and fault finding there, I was told that there were some good tech guys on here that might be able to help identify the cause of my non starting - any information would be useful right now James (Message approved by david_gore) | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 896 Registered: 6-2006 |
Hi James, are you getting switching at the coils? Feed at the coils? There is a voltage control relay for the engine management. ( next to the ECU with a fuse situated on the top) These give quite a lot of problems and are worth a look at. You can ensure the car is not over charging and then bridge it out or check it is giving a 12v output. There is also a gravity / accident cut off, but you should still get a spark (I think)if it is activated. | ||
| James Seaman Yet to post message Username: jseaman Post Number: 1 Registered: 12-2012 |
Paul, Thanks for the response - some additional info for you is that the king lead was generating a spark when the key is moved to the accessory position but then doesn't spark when cranking. I have got two new coils as a matter of course but I don't expect these to change much. There is voltage on the LT +/- of the coil but I haven't checked for switching - will do that and report back, I presume the + collapses to ground or similar/ I popped the voltage control relay off to check this out too, I felt it clicking but thought I would change it anyway (so far haven't matched the part). The gravity feed is the little black box with the pop up bit in it? If so then I've tried in both positions but figured the down position was the correct one? Thanks James | ||
| James Seaman New User Username: jseaman Post Number: 2 Registered: 12-2012 |
I fitted the two new coils this morning and it hasn't changed the problem. I get +12V at the LT coil +ive terminal when the key is in the ACC or cranking position. The -ive terminal has a ~10 Ohm resistance to ground on the engine when off and this increases to ~150 Ohms when in ACC or cranking. I'm assuming either the + or - side of the coil should be switching? I followed the brown wire which is the negative feed to both coils (then paralleled up using a black wire) and it goes immediately to the LPG ECU so I wondered if that could be a possible problem. Where would the feed normally come from? (I mean specifically, which loom and where do I find it). The Zener relay with the 10A fuse all seems good, I've stripped it down and there is a small amount of deposits which I cleaned off the PCB but all looked OK in there Note I still get a spark when I initially move the key to ACC and the relays are buzzing but when cranking I get nothing James | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 897 Registered: 6-2006 |
I think the negative should switch giving the spark. Would need to double check on the wiring diagram . Turning off the ignition collapses the magnetic field and produces a spark. Where was the sensor you changed located? | ||
| James Seaman New User Username: jseaman Post Number: 3 Registered: 12-2012 |
paul, I was expecting similar - do you know where the control wire runs, is it straight to the Bosch ECU normally? I changed the crank sensor which is by the harmonic damper at the front of the engine (and both coils) James | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 898 Registered: 6-2006 |
Check the engine speed sensor for a signal and that it's got a good connection. It's mounted underneath in the bell housing with the connector above it near the top of the engine. The chassis number you quote must be wrong. There should, I think, be two amplifiers slightly behind the coils. Rarely go wrong - especially both at the same time. PM me if you could do with a manual. | ||
| James Seaman New User Username: jseaman Post Number: 4 Registered: 12-2012 |
Paul, thanks for the info - where abouts would I find this connector for the speed sensor and what signal should I see on which wires? I've checked the chassis number against the v5 and it definitely says SCBZE00A8MCH35126 I figured two circuits failing at the same time was unlikely and the fact it sparks during the initial ACC phase means it is CAPABLE of generating spark but not doing so I'll drop you a PM! Thanks again | ||
| James Seaman New User Username: jseaman Post Number: 5 Registered: 12-2012 |
I have checked a number of items on the ecu including coolant sensor, cranking voltages etc, everything is within spec. Could anybody advise where the negative wire for the coils goes to on a car without lpg? | ||
| gordon from jersey Unregistered guest Posted From: 82.112.138.192 |
There have been issues with similar model cars that if engine only fires as long as key in cranking position, then dies when key let go into normal run position. By earthing EACH head with it's own earth strap to the body (even though the main engine earth to block is good) sorts problem. I do not understand the reasons, but know it has worked on at least two cars (Message approved by david_gore) | ||
| James Seaman New User Username: jseaman Post Number: 6 Registered: 12-2012 |
Gordon, thank you for your input. The car only sparks when in the run position not when cranking so not quite what you describe. I had heard of the issue you mention though, apparently it was due to a missing earth strap on one side of the engine. I tried running a jump lead between the chassis and block just in case but it made no difference sadly | ||
| James Seaman New User Username: jseaman Post Number: 7 Registered: 12-2012 |
The ECU error code reading procedure is definitely not doing what it should. I have tried bridging the relay with the 10 amp fuse in it but that didn't alter the behaviour. Someone suggested that the rear sensor for RPM could be the cause so I took it off and it is the same sensor as the front cps so I put my old front sensor (replaced with a brand new one) onto the bell housing and it still doesn't work. Question though - how sensitive is the rear sensor to location i.e. if the shims were not matched then would it cause a lack of spark and what is the clearance supposed to be? Thanks James | ||
| James Seaman New User Username: jseaman Post Number: 8 Registered: 12-2012 |
Finally made it run! It took a lot of time but it turned out to be the fuse to the ecu being partially blown and melted together causing only 8.5V to appear on the ecu supply |
