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MG Midget and Sprite Technical Sick Frog BBS discussion at MG-Cars.net
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MG Midget and Sprite Technical - Sick Frog
| Hi, I was taking a "mature" neighbour out for a spin in the Frog a few days ago when the car began to splutter and die on a slight upward incline. Oh-oh I say, I think we must be running out of fuel, though I'd reckoned there was about a half a tank left. She laughed and replied "it's nearly 70 years since a man last tried that with me!" Made it home, just, car running ok on the flat but spluttering on any gradient so reckoned it was a fuel pick-up issue. Checked fuel line, the clear in-line filter was empty and no fuel pumping through. But it took only two gallons to top up the tank to full. Checked for blockage, none. Checked for vacuum lock in the tank, none. Checked all fuel line unions, tight. But after an hour or so the car started and ran normally in the garage. Out for a run again and once under load the same problem after a couple of miles. Faulty mechanical fuel pump? - fitted an electric pump temporarily, stripped and cleaned the carbs and float-bowls (not that they needed it) and again she ran for a mile or two and then spluttered to a halt. A tow home and into the garage again and car started and ran normally for over an hour though the fuel filter appeared to be empty most of the time and a lot of bubbles being pumped in. Back to the mechanical pump and same result. Engine is a 998cc (not 948) Frog (Mini pistons), 12G206 Head, Swiftune cam, LCB and twin 1-1/4" SUs running a C/R of about 10:1. Electronic Ignition (SimonBBC) and standard coil. She has run faultlessly (more or less) for five summers and now I'm tearing my hair out. I'll try a coil swap on Monday just in case, but am more or less resigned to this being a problem inside the fuel tank. Any bright ideas? thanks for listening dennis |
| D Stanfield |
| I had a similar thing on a honda accord about 25 yrs ago now(doesn't time fly !) it would just come to a halt for no apparent reason. After changing the elec pump twice with no improvement it turned out to be a kink in the fuel line. When you put your foot down or going up hill the restriction stopped enough fuel getting through but when sat idling or just in normal traffic it is ok. |
| Andy Phillips (frankenfrog) |
| Hi Andy, Time sure does fly and flies faster the older you get. That's a really unusual fault, a simple one that you'd never really think of. I did check all the fuel unions but not full lengths of the line, will do so tomorrow. cheers dennis |
| D Stanfield |
| Mechanical fuel pump??? Thats a new one I wasnt a were of... but I know very little about anything beyound the 1275 It almost sounds like fuel evoperation due to the heat, BUT you said you have had the car for 5 years and this is the 1st time this is happeneing For grins... check the fuel cap isnt bad, not venting...not a top 10, but it does happen, check you valve lash, it may have closed up on you, check your coil for being really hot, check that the chock isnt sticking, check you dont have worn butterfly spindles or other carb/intake manifold vacume leaks... Did the tach jump around alot (if its an electronic tack and not a mechanical tach) Basically do the simple check stuff then if nothing obvious narrow it down to a system, fuel or electric This is one of those issues that just takes time and the problem is always somethig really stupid, the better your process of testing and eliminating issues the faster you will find the issue A minor crack in the fuel line is rare, but we have seen it here on more then several occasions But I have to say, te best results come from a good detailed plan to approach dignoises, I normally do a highlight once over of the possiable high probabilities of known issues, if nothing jumps out as obvious, then I start with electirical to determin if the issue is electrical or fuel related...if its still electrical then I follow that path if diagnoises is fuel then I change course and follow that path and keep notes on where ive been, and did Prop |
| Prop and the Blackhole Midget |
| Being that your car is a mechanical.fuel pump and you have a electric pump on stand by Id start there.. hook up.the pump to a 2 gallon gas tank aand then straigt to the carbs with new hoseand drive arond for a while... if the same problem happens you can eliminate the pump and the old hose and fuel cap.and gas tank, as the issue so the most likely problem will be ither carb /// manifold related or the electrical system A quick check of timing, valve lash and compression will illiminate alot of other possiabilities Remember, the more areas you eliminate the closer you are to finding the solution...and trust, me, it will be stupid and you will smack yourself in the head for it Prop |
| Prop and the Blackhole Midget |
| D Stanfield, Had a spitfire act like that, I cant remember if a frog is all steel line or not but change the rubber lines....I found out after many trials that the rubber line would collapse in on itself blocking the fuel. The rubber was worn out but didn't leak. I'm thinking along these lines because you say the filter wont fill... That may be the tip off! These guys are inferring straw effect (hole in the straw) Look for that too! Let us know what you find! Good luck and maybe you can find some younger women to test drive with! :-) |
| Steven Devine |
| Yes, specifically look for weakened rubber fuel pipes upstream of the pump. That is between tank and pump. Small cracks in the pipe won't let fuel leak out, but do allow air to be pulled in, especially when the pump is sucking fuel in fast to keep up with fuel demand on a labouring engine. |
| Guy Weller |
| Thanks for the replies folks. Andy, I checked the fuel lines and no kinks or blockages, unfortunately. Prop, the Frogs and early midgets had a mechanical pump as standard. Flexible fuel hoses are all ok, there's only short lengths to and out of the pump and when test-fitting the electrical pump I renewed those as different lengths were needed, and took care to keep the lines as far from heat as possible. Guy, we are thinking along similar lines, sucking air somewhere, but can't find any problem outside the tank, leaving me with the feeling that there is a problem inside the tank. Steven, the fuel line is one length of copper from tank to front cross-member with only 8 or 9 inches of fuel hose to the pump. I do usually have a younger woman in the passenger seat, but for the moment she's acting as my recovery service. I'll have another go at the lines and pump today but may drop the tank tomorrow to have a look inside. thanks dennis |
| D Stanfield |
| Dennis, Another possibility would be a split in the diaphragm in the pump. They then still work, but at a more leisurely rate which doesn't then keep up with the engine demand. Ohh, no, I see that you tried changing the pump. Forget that comment. The blocked filler cap that Prop mentioned I think could be another culprit in limiting the fuel delivery. Its just that with air in the filter (there is almost always some air, just a little IS ok) it does suggest that the pump is sucking in air rather than fuel, and splits or faults in the rubber hoses is the usual source of this. |
| Guy Weller |
| In this hot weather, I wonder whether the mechanical pump is causing fuel vapourisation. Because the pump is at the engine end, it "sucks" rather than "blows". The pressure in the fuel line between the pump and the tank drops below atmospheric which reduces the vapourisation point in the fuel and, if it's warm/hot conditions, more and more turns to vapour rather than being liquid. |
| Graeme W |
| If Nigel piped in right now, Where are you Nigel this is your cue! He would tell you to check your rotor on the distributor cap. There have been some bad replacements made. He prefers this guy for fixes and recommends them all the time! :-) http://www.distributordoctor.com/red-rotor-arms.html Glad to hear your keeping an open mind to more earlier models of woman! Ahhh!......freakin Nigel must have brain washed me to post this.....Subliminally! |
| Steven Devine |
| Coil swap is a good idea - and it's so easy to interchange them at the roadside. If the new coil seems to solve it, a quick swap back to the old one will tell you whether or no. |
| Nick and Cherry Scoop |
| To do -coil swap -flexible fuel lines collapsing inside (not suited for modern fuels)DO NOT FORGET THE OVERFLOW PIPES!!!! -pumps -cracked fuel pick up pipe replace tank Follow in that order and you will find the problem |
| Onno K |
| Good grief, Its like everyone is speaking from experiance....is that a good thing...??? Haha Prop |
| Prop and the Blackhole Midget |
| Thanks guys for the ideas, unfortunately I didn't manage to get as much time in the garage today as I'd hoped, life does tend to get in the way. But hoping to spend some time there tomorrow. Looks as if it's just going to be a case of double-check everything. Hadn't thought about the rotor arm or distributor cap Steven but think I have spares so will try those to rule out that possibility, just in case. dennis |
| D Stanfield |
| I guess Nigel was busy at home beating his wife! Goodluck Dennis! |
| Steven Devine |
| I guess Nigel was busy at home beating his wife! Goodluck Dennis! |
| Steven Devine |
| Steven, I can tell you with all honesty and without any shame that the mere thought of me beating my wife could bring tears to my eyes easily I'm not a physically violent person but I'm sure under some circumstances I could be but never in a million years to my wife, perhaps to any person that caused her harm I do joke with my wife about her being my married chattel and the rule of thumb but we've been together long enough to know these are jokes |
| Nigel Atkins |
| Dennis, did you try taking the petrol cap off when you had the trouble to see if the car would run again along with rotors and dissy caps and HT lead set and its connections, sometimes connections or wires break down or perform badly when hot or the fault shows up more when hot I also mention the delicate leads of the electronic igniter possibly getting chaffed inside and outside the dissy cap though I can't think why this would only cause problems when hot unless in combination with another fault I can see it now but I think you put summer use which if so leaves many months of each year with the car not used possibly build up gremlin to discover when you do use it more regular year round use would probably help the car - there are many more good driving opportunities on often dry and sunny day in late autumn, winter and early spring than in summer or just either side of summer when we have more unpredictable and possibly heavier rainfall |
| Nigel Atkins |
| Nigel, interesting that you should mention this: "I also mention the delicate leads of the electronic igniter possibly getting chaffed inside and outside the dissy cap though I can't think why this would only cause problems when hot unless in combination with another fault." I had exactly that problem, and discussed it here on the BBS at the time. The single wire feed to the electronic module on my 1275 Sprite(ex MG metro unit)behaved exactly that way. Misfiring when hot, running perfectly when cold. The copper strands inside the insulating plastic had broken, whilst the insulation itself remained intact so there was nothing visibly wrong. But when the plastic warmed up it went floppy, allowing the wires inside to break contact. When the cable cooled again the plastic insulation became more rigid and the wires inside maintained contact. It was a devil to diagnose that fault! |
| Guy Weller |
| Hi folks, latest status report is no change, unfortunately. Have checked over/swapped out various parts of the ignition side, checked timing, etc. but the patient shows no improvement. I did find some references to similar problems in the archive back about 2003, and on another BBS, that seem to mirror my problem and, as suggested by Guy earlier, all relate to air being drawn into the fuel line, mostly at the tank connection. I had another look at that union and, while tight the nut is tight up against the flange so it's not clear if it is tightening on that flange or on the "olive" in the pick-up pipe. However, on removing this the PTFE tape was a bit soggy suggesting petrol was getting past the olive seal and, by inference, air could go the other way. I remade the joint using gas-fitters PTFE on the nut threads (this is resistant to petrol) but thinking about the design of this union the only possible point of seal is the olive, sealing the threads with tape or, as has been suggested in the past, with Loctite would appear to be of no benefit in any case. I've ordered up a new pipe to see if that will seal more effectively on the olive before closing up on the flange, but if not may drop the tank and bring it to a repairer to have a more sensible pick-up line arrangement installed. Watch this space. dennis |
| D Stanfield |
| Guy, I didn't remember that one or can faulty remember if another one was HT leads or LT leads breaking down or connections coming loose when hot. I'll pretend I covered yours in my general wires breaking down when hot comment but then have to admit contradicting myself when I put I couldn't see why the it would only happen when hot unless in combination with something else. I now know it could be the delicate wires but unfortunately fear I won't remember this, or the details of HT or LT wires, later, I'll just have as usual something tickling the back of my mind but unsure what it is or whether its memory or imagination. It does mean I can watch films again without knowing the outcome or exact details. :) |
| Nigel Atkins |
| I had similar symptom once on my 1500, after much changing of parts it turned out to be the rubber pipe on top of the gearbox which was age softened and closed up under load. A good way to check for leaks front to rear is to temporaily fit a pusher type pump at the rear, that'll soon expose any splits in the pipes or rubber hoses between the tank and the mechanical pump. |
| SR Smith 1 |
| Nigel, I wasn't reminding you. Or expecting you to remember my specific problem! I was simply saying that your comment about a possible faulty wire to the electronic module was a good suggestion. And that I had experienced just such a fault myself, in a situation where the fault was temperature dependant. |
| Guy Weller |
| Dennis, forgot to say IIRC pick up pipe in take getting blocked and then unblocking itself has come up before ptfe tape on the threads could go both ways making it easier to thread the nut or more difficult, as you say it's the olive that (should) seal I've gas-fitting ptfe tape from 20+ years ago and some from B&Q possibly 10+ years ago, the earlier proper stuff is like tape and the later DIY stuff is more tissue paper like, as I put both can have there uses but I'd check the new use of ptfe and if you still have a leak I'd remove the ptfe and try without some sort of petrol resistant pudding or sealant stuff might seal between the olive and nut I've just used Hyomar Hylotyte Red 100 to good effect (so far anyway) for curing you might need the use of a hair dryer or you might use one of their other products - http://hylomar.com/hylomar-product-range/gasket-jointing-compounds/#hylotytered |
| Nigel Atkins |
| Hey dennis, In the mean time while your waiting for parts.... Consider my suggestion...of a 1 or 2 gallon gas can attached to your electric fuel pump and a new hose from the pump to carbs, and just drive car for 15 to 20 miles and see if the problem presist If the problem persist it will tell you alot about the problem and what to look for next, If the car now runs fine, then you have narrowed the issue down significantly Its easy to.do, fast and seriuously cheap being you got the parts Also if you you can be a little more detailed on what you did and the parts you replaced, it keeps us a little more focased on the process and cuts down on our guessing But I give you a bronze star for staying motivated and quick on the draw....thanks for getting back so quickly Prop |
| Prop and the Blackhole Midget |
| my internet connection went down again so - ETA: Guy, yes I did know that, I was being a little self-deprecating for not putting the facts together or more honestly just not remembering it from the last time I saw it yes we are agreeing black is black and white is white and there are many area of grey in between - but that is not an invitation or feed line for your joke again |
| Nigel Atkins |
| Black is black and white is white.... Sounds like someone has read the book 50 shades of gray....nigel have you purchased the movie tickets yet ??? Oh wait, you probably cant remember...hahaha Prop |
| Prop and the Blackhole Midget |
| Prop, I don't think it's the type of film I'd watch let alone enjoy for the last 17 years I've been able to go to the cinema where my wife works for free but I very rarely go and can't remember the last time I went but it would be years ago ironically before she started work there, and I paid to get in, I'd perhaps sometimes go twice or more a week, films changed much more frequently then and they showed very few 'blockbusters' |
| Nigel Atkins |
| Nigel, I here ya, I used to love movies and went minium once a week, but maybe 10 years ago, movies just started to suck, now I go maybe 3 times a year, and even thats a crap shot. The last 3 films I saw was planet of the apes, great film, noah... worst film of the year, and the 1971 F1 race film...decent So im batting 50/50 at the moment What ive found in determining if a film is good or bad based on just the previews, is to pay attention to the dialoge, if its over the top and chessy, then watch this bomb on dvd, if the dialoge in the preview is normal, not jumping the shark, and converstional...then there is a good chancethe film will be good And if its a superhero comic book movie... Im walk away Btw... did you hear that Thor is now had a sex change and has become a woman... yepp a chick wannabe without a dick, (im not jokeing, very real) (By the Beard of asigard...) hmmmm... I dont think so ! Prop Prop |
| Prop and the Blackhole Midget |
| My 1275 was having similar problems, thought I was out of gas, called my Sprite "expert". He said was probably crud in the tank blocking the pick-up screen. Told me to shack the car back and forth....she started up and I made it home. Ran it a few days later , after couple miles same thing happened, but shacking didn't help. Disconnected the fuel line and blew into line and it cleared enough to get home. Dropped the tank and it was in bad shape...a new one is on order. |
| Kth Hurt |
| I ran into that this spring... I used an air compressor 25 psi and blew thur the pipe and cleared the blockage in the tank and its still working good today Prop |
| Prop and the Blackhole Midget |
| Vote for crud in tank and compressor back-blast. Had a lobster boat years ago with iron fuel tanks, after spring commissioning after about ten hours on the clock engine could only give 50% power. Filter loaded with rust crud, even stored for winter with full tanks,new filter then fine for the season. I've used an outboard motor tank with an electric pump as a diagnostic tool in the past. Sounds like maybe the opening choke leans your mix Good Luck |
| Bob Ketcham |
This thread was discussed between 27/07/2014 and 08/08/2014
MG Midget and Sprite Technical index
This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.