| Author | Message | ||
     Carl Jensen Experienced User Username: carl_jensen Post Number: 46 Registered: 2-2005 |
The electronic fuel pumps on my Shadow are under 3 years old and have about 5K miles on them. On my last 3 trips in the car they have quit working after about 45 minutes of driving in the hot Texas heat, but then worked again after about 30 minutes to let the engine cool some. Same thing happens again in about 30 minutes. This has happened to a lesser degree (pumps didn't fail completely but the engine would lose a ton of power and act like it was starving for gas) over the last 20 years but was so intermittent that I couldn't diagnose the failure. Now things are much worse with the hot pumps failing completely during my last 3 outings. When this happens the pumps don't click at all as they normally would when I am about to start the car, but my voltmeter shows that both pumps are being supplied with power right at the pumps during the failure. However, the possibility of both pumps failing and then working again simultaneously seems impossible. I recently changed out the oil pressure sending unit in case it was going bad and causing the power to be cut from the pumps, but if that unit was bad then I believe there would be no power to the pumps when they failed. I have also recently changed out the main fuel filter and small filters on the carbs. In case there was blockage I also drained a bit of gas from the gas tank drain plug as well as blowing compressed air back into the tank via the fuel line that goes from the tank to the main fuel filter. Do you have any idea on why this is happening? I have a new set of pumps on the way just in case, but this makes no sense. Any help would really be appreciated since I am totally stumped (as usual). Thanks, Carl Jensen | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 962 Registered: 6-2009 |
Carl, I'm wondering if you may be the victim of "bad electronics" and having had the pieces come from the same production run with a component that's failing in the same way. The fact that this is happening consistently after 45 minutes driving from cold in hot weather, and 30 minutes later if starting from "cooled warm" makes me suspect one of the electronic components for each pump fails once hot. Never having had one of these units to do a postmortem on, that's as far as my theorizing can go. Have you tried carefully, and with a catch bottle at the ready, pulling the fuel line in the engine bay immediately after failure to proceed? [You can do this with the car key in the "Run" position but the engine not running.] If you have fuel flow at this point in time it would at least let you confirm definitively that it's not likely a pump problem. The pumps won't click if the carb float bowls are already full and the floats are cutting off further fuel. If you've somehow got a "stuck closed" float (and two of these would be odd, too) your pumps might be OK and checking to see if they pump when there's nothing to create the back pressure that makes them stop until it's released should help you to rule in or rule out the pumps. Also, is there any possibility this might be a problem from modern fuels, which are significantly more volatile, and engine bay heat causing the fuel to boil in the float bowls, effectively starving the carbs of fuel? Brian, who completely relates to your "totally stumped" sensation and always hopes I'll never have it again [Good luck with that!!] | ||
| Randy Roberson Prolific User Username: wascator Post Number: 284 Registered: 5-2009 |
Electronics can indeed be sensitive to temperature changes and fail willy-nilly. I agree with Brian also on the possibility of vapor lock. What about ignition failure? Are you positive it's fuel and not ignition? Coils and other (electronic) ignition parts can fail when they heat up. If the ignition fails, the pumps won't run because the carbs are full. Like Brian says.. | ||
| richard george yeaman Prolific User Username: richyrich Post Number: 197 Registered: 4-2012 |
I agree with Randy Ignition is the probable cause most likely suspect would be the Ballast resistor both the coil and the Ballast resistor are tucked in at the back of the engine in the hottest place imaginable after 40 years the wire in the Ballast resistor rusts almost through and when it heats up it stops supplying power my 1974 shadow had a similar problem hope this helps. Richard. | ||
| Bob uk Unregistered guest Posted From: 94.197.122.79 |
This is a rare fault because this is the first time I have heard of the electronic type of SU pumps giving trouble. I would remove the pumps and test them at 13.5 volts. use kerosene or derv as fuel Run pump for a while and see what happens. If a restriction is placed in the outlet pipe it will slow the pump to more like it would be in service Check the temperature of the pump as it goes. (Message approved by david_gore) | ||
| Randy Roberson Prolific User Username: wascator Post Number: 285 Registered: 5-2009 |
I had this exact ballast resistor problem on the '86 Jaguar. Tossed the br and all was well. The previous owner had spent much $ and foul words to no avail. | ||
| Bob Reynolds Prolific User Username: bobreynolds Post Number: 141 Registered: 8-2012 |
When this happens you can easily check the ballast resistor by checking that there is 12v on the coil, in the same way that you checked the voltage at the pumps. I would recommend changing the ballast resistor every few years anyway. It is one of those components that will leave you stranded in traffic when it packs up unexpectedly (and it will!). | ||
| Carl Jensen Experienced User Username: carl_jensen Post Number: 47 Registered: 2-2005 |
Thanks very much everyone for your advice. Looking at electrics other than in the pumps sounds like a good way to go. The ballast resistor/coil/electronic distributor components have been replaced in the past, but after owning the car for 25 years these components could very well be suspect. Since my new pumps are already on the way, I will replace them and if the problem persists then I will investigate these other options. Thanks again for everyone's help. I will report back in a couple of weeks and let you know what has transpired. Thanks, Carl | ||
| Bob Reynolds Prolific User Username: bobreynolds Post Number: 142 Registered: 8-2012 |
I did once actually toy with the idea of making up an electronic circuit to monitor the pulses of current going into the fuel pumps. The idea was that if these pulses stopped for any reason, it would light up a warning on the dashboard. It could be teed into the Low Fuel warning light. If the warning light came on, you should still have enough fuel in the float chambers to get to the side of the road, and just as important, you would instantly know that it was a fuel problem and not ignition, so your roadside diagnostics would be greatly simpified! Also, if the car stopped for some reason and the light didn't come on, you would know that it was an ignition problem and not fuel! This would be a very useful addition, but it didn't get any further than an idea. I have seen similar ideas that bring up a warning if the 12v supply to the pump fails, but this will not warn you if the pump itself fails to pump. | ||
| Mark Aldridge Prolific User Username: mark_aldridge Post Number: 144 Registered: 10-2008 |
Bob, I have heard of both the electronic and points SU pumps failing.I ditched them in favour of Facet interrupter pumps with pressure regulators on all of my cars long ago. Mark | ||
| Bob uk Unregistered guest Posted From: 94.197.122.90 |
The SU pumps are simply supplied with constant volts not pulses. It would be possible to put an led light across the points of a electro mechanical SU pump. When the light is on means points open and carb full. SU means skinners union (Message approved by david_gore) | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 970 Registered: 6-2009 |
Mark, I long ago added the Facet Red Top pump to my resources list as an alternative to either the dual SU or Pierburg rotary vane pump. I'm just curious which Facet pump you're using and which pressure regulator. From what I've been able to determine it seems the Red Top is probably a bit of overkill when compared to the flow rate and pressure of the original SU or Pierburg pumps. Brian, who has SU on SRH33576 and Pierburg on LRK37110 | ||
| Mark Aldridge Prolific User Username: mark_aldridge Post Number: 145 Registered: 10-2008 |
Brian, Facet red top, with filterking regulator set to 3.5psi on my Shadow and Bentley S1,Facet fast road cube set at 1.5psi on my MG midget 1500 and Austin Healey Sprite 1275 . My Mulsanne is on a Pierburg pump.We have also used the Facet red top and regulator on my son's V12 Jag and his MK1 Jag set at 3.5 psi.I carry a Facet cube pump in my tool bag in case of a pump failure, which I have used when the Jag SU failed and when the Midget mechanical failed. | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 971 Registered: 6-2009 |
Mark, Thank you for the detailed information. I shall "fill in the blanks" in my RR & Bentley Parts, Repair, Restoration & Other Resources Compilation and upload the new revision shortly. Brian | ||
| Bob uk Unregistered guest Posted From: 94.197.122.71 |
I have heard of facet how do they work inside. There is one on their website that costs £39 and is 1.5 to 4 psi. 25 gallons an hour at 12 inch prime which is I assume lift. Even if the lift is more I should think that it will just be less capacity. Which means the pump will not supply enough fuel to drive at 120 mph. I didn't realize they were that cheap. In view of this, any SU troubles go facet it's a no brainer. (Message approved by david_gore) | ||
| Bob Reynolds Prolific User Username: bobreynolds Post Number: 143 Registered: 8-2012 |
"The SU pumps are simply supplied with constant volts not pulses." They are supplied with constant 12v but the current is not constant, it is pulsed as the coil is energised. These pulses can be monitored. | ||
| Mark Aldridge Prolific User Username: mark_aldridge Post Number: 146 Registered: 10-2008 |
Bob, there are two types of Facet pump. The interrupter type is capable of 250bhp+ and is quieter than the cube type. The cube type can be lift height sensitive but a version is available with 36 inch lift capability.Lift height is not relevant on Shadows, Spirits, Clouds as the pump is mounted under the car and thus gravity fed, or has very little lift height.We have used a cube type Fast road on the limit of its lift at 175bhp with no starvation on a Jag. Mark | ||
| Bob uk Unregistered guest Posted From: 94.197.122.76 |
Forgot about the amps. SU pumps had 2 types ones that are fitted higher than the carb and ones that are low down. So I guess that the prime height is what facet use. I know that on SUs mixing the two up causes problems. I think an led across the points would be a easy and quick and cheap way. Or fit a 0 to 10 amp ammeter in series. SU pumps look nicer and have an elegant shape especially a double pumper. The Facet pump needs fins or something to give it the look. (Message approved by david_gore) | ||
| Carl Jensen Experienced User Username: carl_jensen Post Number: 48 Registered: 2-2005 |
I just installed a new electronic fuel pump and it seems to have cured the problem of the engine dying after it gets hot. I don't really understand why the fault appears to be temp related, but the new pump "clicks" more rapidly than the old pump. I'm not sure why I only got 5K miles/3 years out of the last pump, but it may have been a reconditioned unit(?) that wasn't rebuilt very robustly. Thanks very much to everyone for their suggestions. I wouldn't have been able to keep my Shadow running over the years without the help from people on this forum. Thanks, Carl | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 1020 Registered: 6-2009 |
Carl, Did you do any sort of post-mortem on your old pump? [Scratch the bits I'd had here regarding points-type SU pumps, since you'd said that the original pump in question was electronic. I'd still be curious whether a post-mortem might turn up something that explains what was happening.] When you say "new electronic fuel pump" do you mean a dual SU with the electronic equivalent of the points or did you go with an alternative? If an alternative, which one did you install? Brian | ||
| Carl Jensen Experienced User Username: carl_jensen Post Number: 49 Registered: 2-2005 |
Brian, the pumps were SU electronic units. The vendor assures me that it is new. I will probably not do a post mortem due to time and health constraints, so I guess the failure will need to remain a mystery for now. However, my experience has been that my mysteries tend to come back and bite me over time. Thanks, Carl | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 1251 Registered: 6-2006 |
Hi Carl, make sure that there are no restrictions to the feed. Either blocked filter, collapsed hoses or bent pipes. Most often there is something that causes the Su's to fail. And it will come back to bite you as you say. Shadow I's suck through the filter and lines so any restriction slows the pump and keeps the coil energised for much longer than it should be (and is designed to be). Causing everything to get overheated. Shadow II's pump position was modified to push through the filter (and the majority of the fuel lines) so any restriction will put the pump into it's off state instead of keeping it in the on state. PITA to get to though.:/ Boost starting/Charging can damage the electronic type. Getting jump leads on the wrong way can damage both types. | ||
| Jan Forrest Grand Master Username: got_one Post Number: 644 Registered: 1-2008 |
"Shadow I's suck through the filter and lines so any restriction slows the pump and keeps the coil energised for much longer than it should be (and is designed to be). Causing everything to get overheated." That's just one more of the 'quiet upgrades' performed over the long lifespan of the Shadow 1. My '76 model pushes the fuel through the filter. | ||
| Bob uk Unregistered guest Posted From: 94.197.122.88 |
My pump is a SU sucker. My car has a filter in the tank a filter by the tank a filter in the SU pump and a filter in each carby toot. I was thinking of fitting another to the main filter just in case RR didn't fit enough filters. (Message approved by david_gore) |
