TR5tar Posted September 21, 2014 Report Share Posted September 21, 2014 Apologies if this is a common problem and has been covered elsewhere on the forum. Pushing along at a steady 50-55 recently, I crossed over some recessed train track which made the car bounce up and down a bit. Then, just for a 3-4 seconds, I lost power, although the engine didn't cut out. The car had plenty of fuel in it, so there was no issue there, but someone I spoke to about the problem thought that it could have been the fuel pump. I've not had the problem since, but then I haven't gone over any major bumps at speed since. Is this something that others have experienced? Is it a sign of something more serious to come? Is it something that I can cure (other than going more slowly over bumps)? Thanks, DC Quote Link to post Share on other sites
PJM Posted September 21, 2014 Report Share Posted September 21, 2014 Loose electrical connection somewhere? Pump connections, relay, earth, inertia switch, fuse? Quote Link to post Share on other sites
TR5tar Posted September 21, 2014 Author Report Share Posted September 21, 2014 Thanks PJM. I think all your suggestions are a possibility, and I did wonder about the connections, but I think what the chap who mentioned the fuel pump was getting at was something about the magnets in the pump, but I don't understand pumps enough to know how they work and what part the magnets play. By the way, in case anyone was wondering what a "bumpo" of the title is, it's a bump that you go over and at the same time shout "Ooo", not a typo, honest. DC Quote Link to post Share on other sites
Rodbr Posted September 21, 2014 Report Share Posted September 21, 2014 What car? What carbs? type of fuel pump? Quote Link to post Share on other sites
North London Mike Posted September 21, 2014 Report Share Posted September 21, 2014 Just a thought............ Wheels off the ground ? Quote Link to post Share on other sites
graeme Posted September 21, 2014 Report Share Posted September 21, 2014 What car? What carbs? type of fuel pump? Could be a TR5, clue in the posters username. Graeme Quote Link to post Share on other sites
TR5tar Posted September 21, 2014 Author Report Share Posted September 21, 2014 Yes, TR5, so no carbs, PI. I don't think the wheels were off the ground, but it was more of a bump than I was expecting. Thanks, Darren Quote Link to post Share on other sites
roy53 Posted September 21, 2014 Report Share Posted September 21, 2014 It's only TR5 prices that fly ROY Quote Link to post Share on other sites
Rodbr Posted September 21, 2014 Report Share Posted September 21, 2014 Graeme, He could have been driving something else, so your comment is not really helpful in any way. Hi Darren, How much fuel was in the tank, perhaps your fuel became airbourne and the pump got a gulp of fumes insufficient to stop the engine but total lack of power momentarily till pump started on fuel not fumes. Quote Link to post Share on other sites
Peter Cobbold Posted September 21, 2014 Report Share Posted September 21, 2014 Inertia switch. Doing what its supposed to do but rather too enthusiastically. Quote Link to post Share on other sites
TR5tar Posted September 21, 2014 Author Report Share Posted September 21, 2014 (edited) Hi Rodbr, I was on just over 3/4 of a tank when this happened. I try never to run with less than half a tank, as I'd heard that this could cause problems on a TR5. And so, I don't think it was lack of fuel that caused this particular problem, but thanks for the thought. Hi Peter, I must confess I don't know what an inertia switch is. Is it a safety device which cuts the flow of fuel if the car is in an accident? If so, then I'm beginning to see how this might have caused the lack of power. You say that it's being a bit over enthusiastic. Does that suggest that it's faulty? Is it something I should be concerned about, or is it quite a common thing? Thanks, Darren Edited September 22, 2014 by TR5tar Quote Link to post Share on other sites
Peter Cobbold Posted September 21, 2014 Report Share Posted September 21, 2014 Darren, The inertia switch cuts the electrical feed to the fuel pump in the event of a collision- so we dont get 100psi fuel sprayed around. Its a grey plastic cylinder next to the wiper motor on the nearside bulkhead. Normally a button on the top pops up when the cut out has been activated. But yours might not have been triggered hard enough to do that. It has given problems on TR6s, cutting out when drivng normally, and a modern substitue has been found. So.....if your cutting out recurrs when attacking that railway line again then try connecting the two wires at its base together making sure you insulate them from earthing to the body ! If that stops the cutting out then you have found the problem. If not then you have the fun of finding some other fault ! Intermittent faults can be infuriating so having a reliable way of triggering it will help. Peter Quote Link to post Share on other sites
Kiwifrog Posted September 22, 2014 Report Share Posted September 22, 2014 (edited) If I remember correctly inside the inertia switch is a heavy ball bearing held into contact with 2 electrical contacts by a weak spring, therfore a big bump could momentarly cause the bearing to bounce and lose contact for a fraction of a second stop the pump causing low fuel pressure and the problems you describe. Not something I would personally worry about, although if I were you I would make myself familar with the cutout switch and how to reset it in case next time it pops all the way up. Cheers Alan Edited September 22, 2014 by Kiwifrog Quote Link to post Share on other sites
TR5tar Posted September 22, 2014 Author Report Share Posted September 22, 2014 (edited) Thanks Peter, Alan. This inertia switch certainly sounds like the culprit, and is definitely something I need to be familiar with in case I need to reset it. I've been out to try to locate it, following your guidance Peter, and found a black cylinder with a red, rubber cap in on it, located on the bulkhead, near side. Pictures attached. Is this it? Thanks Darren Edited September 22, 2014 by TR5tar Quote Link to post Share on other sites
ST TR5 Posted September 22, 2014 Report Share Posted September 22, 2014 TR5's we're not fitted with inertia switches Cheers Sean. Quote Link to post Share on other sites
stuart Posted September 22, 2014 Report Share Posted September 22, 2014 The one in the photo is an aftermarket fitting so check the connections to it. Stuart. Quote Link to post Share on other sites
TR Mitch Posted September 22, 2014 Report Share Posted September 22, 2014 Inertia switch. Doing what its supposed to do but rather too enthusiastically. The inertia switch does not usually reset itself, that could be potentially very dangerous. You have to push the button to get it back and I doubt they suffer from intermittent connection otherwise there'd be dozens of modern cars coughing along our bumpy roads. The switch looks very familiar to me (see this post). I think the problem lies elsewhere, perhaps the pump, although I believe there is a decent Bosch pump in the set up on your car Quote Link to post Share on other sites
Peter Cobbold Posted September 22, 2014 Report Share Posted September 22, 2014 Inertia switch. Doing what its supposed to do but rather too enthusiastically. The inertia switch does not usually reset itself, that could be potentially very dangerous. You have to push the button to get it back and I doubt they suffer from intermittent connection otherwise there'd be dozens of modern cars coughing along our bumpy roads. The switch looks very familiar to me (see this post). I think the problem lies elsewhere, perhaps the pump, although I believe there is a decent Bosch pump in the set up on your car MIne would break the circuit without tripping the button - and without going over bumps. Nasty. I would have replaced it with a modern if I still ran PI. Darren's looks like its at an earlier stage f failure owhen it trips briefly and then remakes. But its not the same type as the 6's. Quote Link to post Share on other sites
TR5tar Posted September 23, 2014 Author Report Share Posted September 23, 2014 Thanks ST TR5, Stuart, Mitch and Peter. Although we may not have conclusively got to the bottom of what caused the problem, I've learned something useful and important with this discussion of the inertia switch. At least if I get the problem again, with a total loss of power, the inertia switch is the first thing I'll try. I have to say, I've quite surprised myself by locating the switch (thanks to Peter's direction). I felt sure I'd get several posts telling me the photo was of something entirely different. Darren Quote Link to post Share on other sites
brucer Posted September 23, 2014 Report Share Posted September 23, 2014 Have you tried changing the fuse in the pump circuit? I have had 2 fuses that have had intermittent/poor connections in the end cap. Bruce Quote Link to post Share on other sites
Peter Cobbold Posted September 23, 2014 Report Share Posted September 23, 2014 Thanks ST TR5, Stuart, Mitch and Peter. Although we may not have conclusively got to the bottom of what caused the problem, I've learned something useful and important with this discussion of the inertia switch. At least if I get the problem again, with a total loss of power, the inertia switch is the first thing I'll try. I have to say, I've quite surprised myself by locating the switch (thanks to Peter's direction). I felt sure I'd get several posts telling me the photo was of something entirely different. Darren You found it even with my wrong instructions ! Had to say that in case other 5 owners are looking for a grey plastic cylinder. Peter Quote Link to post Share on other sites
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