S Type R engine cuts out / sometimes won't restart
#22
#23
OP here: well I changed both fuel pumps and the fuel filter and am getting the same “no start”.
Actually, it fired right up initially and ran fine. I tried restarting it a couple of times and it fired. Then, it took a few extra cranks to fire but did start. Now, its not starting at all. Again😡
fuel pressure is 55psi at idle and I think it went up to 70psi or so full throttle.
BTW, for the person who asked; with ignition turned on bit car off psi was 45psi.
Any ideas on what to try next?
Actually, it fired right up initially and ran fine. I tried restarting it a couple of times and it fired. Then, it took a few extra cranks to fire but did start. Now, its not starting at all. Again😡
fuel pressure is 55psi at idle and I think it went up to 70psi or so full throttle.
BTW, for the person who asked; with ignition turned on bit car off psi was 45psi.
Any ideas on what to try next?
#26
With the ignition in the ON position, without engaging the starter, the fuel pressure should be around 3 bar (300 kPa).
#27
The following 2 users liked this post by Todd951968:
kr98664 (06-02-2020),
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#28
Just thinking out loud, wondering if the relay sockets may have been loose or corroded. Do you still have the old relay? Do the prongs show any discoloration from heat? Pop off the plastic cover and look inside for marks from arcing. Once the contacts start arcing, the relay can overheat. Heat can then be transferred to the sockets in the fuse panel. This causes all sorts of problems, such as oxidation or reduced grip. Replace or reseat the relay and the connections might improve enough to last a little while before returning. And depending on which sockets were the worst, the symptoms may even change.
No guarantees, just something to consider. We've had a few oddball faults caused by problems with the relay sockets.
#29
Was this relay the only part that was changed? And after replacement, how soon before all these new symptoms appeared?
Just thinking out loud, wondering if the relay sockets may have been loose or corroded. Do you still have the old relay? Do the prongs show any discoloration from heat? Pop off the plastic cover and look inside for marks from arcing. Once the contacts start arcing, the relay can overheat. Heat can then be transferred to the sockets in the fuse panel. This causes all sorts of problems, such as oxidation or reduced grip. Replace or reseat the relay and the connections might improve enough to last a little while before returning. And depending on which sockets were the worst, the symptoms may even change.
No guarantees, just something to consider. We've had a few oddball faults caused by problems with the relay sockets.
Just thinking out loud, wondering if the relay sockets may have been loose or corroded. Do you still have the old relay? Do the prongs show any discoloration from heat? Pop off the plastic cover and look inside for marks from arcing. Once the contacts start arcing, the relay can overheat. Heat can then be transferred to the sockets in the fuse panel. This causes all sorts of problems, such as oxidation or reduced grip. Replace or reseat the relay and the connections might improve enough to last a little while before returning. And depending on which sockets were the worst, the symptoms may even change.
No guarantees, just something to consider. We've had a few oddball faults caused by problems with the relay sockets.
Got the car home, drove it for a few days, and then the same thing occurred approximately 20 miles later. Fortunately, I was close to home and the engine torque got me the last 2 miles home, albeit at 8 mph.
A search on this forum pointed to a low battery as a place to check. Mine was 5 years old. The voltmeter showed 11.0-12.0 or so. The forum said that 12.5-ish is the minimum threshold for the S Type computers. When it falls below this, computers act up. So, I replaced the battery which is reading 12.45 v after sitting overnight. I am driving the car over the next few days to see if this works.
Recap: I put the car away for the winter in early December. Ran great when parked LOL. In March 2020, I had to recharge the flat battery to get it started. I drove the car a couple of times on short trips (15 miles roundtrip). It started stalling while driving but would restart immediately. Then, it became harder and harder to restart, taking more time. With the pandemic going on and more time on my hands, I changed both fuel pumps, fuel filter, and crank position sensor to no avail. I also replaced the valve cover gasket on the passenger (R) side that was leaking. None of this cured the no-start issue. The way I see it, all of the above items were at 104k miles so replacing them as preventative maintenance , rather than as a repair is OK with me. I am a preventative maintenance kinda guy. It was the independent shop that found the source of the no-start to be the relay. Hopefully, the new battery will solve this latest issue. TBD.
The following users liked this post:
kr98664 (06-04-2020)
#30
Fingers crossed, sounds like you are hot on the trail. Do I understand correctly that the car is behaving itself so far with the new battery? The values you quoted were definitely low. I wonder if your old battery was in marginal health, and it ran down further while sitting in the shop.
Do you have a scanner or code reader? With all the current faults, limp mode, etc., there should be some codes. Beg, borrow, or steal a scanner or code reader so we can get a handle on what the computer is seeing. You're working blind without one, which can get expensive really quickly.
I'm very curious about the relay that was changed, and how it cleared one problem but caused another. The closest I can find to an "ECU relay" is R5 (Engine Management System Control) in the front power distribution box under the hood. The new relay may look different that all the others, so hopefully it's easy to spot. See figure 01.7 here:
http://www.jagrepair.com/images/Elec...al%20Guide.pdf
Relay R5 controls a LOT of stuff for the engine, including the fuel injectors. If failed, it would have probably caused the crank/no-start as you previously had. I have to wonder if the new relay may be better, but still not 100%. You could try swapping with a known-good relay of the same size and see if that helps. The other possibility is like I mentioned earlier, with heat damage affecting the sockets where the relay plugs in. I'd suggest making a test strip the same dimensions as the relay prongs, and testing each socket individually for a proper grip. Also, you should be able to see the tops of the sockets if you get your nose down in the panel. Look for any signs of discoloration, which indicates heat damage.
While you're at it, also check relay R4 and its sockets for any signs of overheating. This is the Throttle Motor Relay, seen in figure 03.5. Your mechanic may have had this relay out while troubleshooting. If not fully reseated, or if the sockets were loose due to overheating, that could cause the current slew of faults you've got. Remove the plastic cover and look inside for any signs of arcing.
Do you have a scanner or code reader? With all the current faults, limp mode, etc., there should be some codes. Beg, borrow, or steal a scanner or code reader so we can get a handle on what the computer is seeing. You're working blind without one, which can get expensive really quickly.
I'm very curious about the relay that was changed, and how it cleared one problem but caused another. The closest I can find to an "ECU relay" is R5 (Engine Management System Control) in the front power distribution box under the hood. The new relay may look different that all the others, so hopefully it's easy to spot. See figure 01.7 here:
http://www.jagrepair.com/images/Elec...al%20Guide.pdf
Relay R5 controls a LOT of stuff for the engine, including the fuel injectors. If failed, it would have probably caused the crank/no-start as you previously had. I have to wonder if the new relay may be better, but still not 100%. You could try swapping with a known-good relay of the same size and see if that helps. The other possibility is like I mentioned earlier, with heat damage affecting the sockets where the relay plugs in. I'd suggest making a test strip the same dimensions as the relay prongs, and testing each socket individually for a proper grip. Also, you should be able to see the tops of the sockets if you get your nose down in the panel. Look for any signs of discoloration, which indicates heat damage.
While you're at it, also check relay R4 and its sockets for any signs of overheating. This is the Throttle Motor Relay, seen in figure 03.5. Your mechanic may have had this relay out while troubleshooting. If not fully reseated, or if the sockets were loose due to overheating, that could cause the current slew of faults you've got. Remove the plastic cover and look inside for any signs of arcing.
#32
#34
What threw me off is that I tested the relay w/a multimeter. It tested ok. But I wasn't having any luck and was convinced it was a fuel problem. Based on this thread I decided to just swap the relay and BAM the engine started perfectly. I swapped it back in and no start. (A -> B -> A test)
Thanks to all who contributed to this thread.
Last edited by wydopnthrtl; 06-10-2020 at 08:47 AM.
The following 3 users liked this post by wydopnthrtl:
#35
I am happy to report that it appears as though the new battery was the final fix! ...........until the next issue arises. Cheers!
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