nylen Posted August 1, 2020 Report Share Posted August 1, 2020 Hi, I have problem starting my TR5. When the car has been i garage for a week or more I have to crank the engine up to 30 sec before It will start on some of the cylinders. After a minute or so it revs perfect on all cylinders. The MU was rebuilt by PDI for 3 years ago and I have had the problem since the rebuild. When the engine runs it works perfect and I have a Lambda of 0,85-0,9. That is perfect. Before the rebuild it was about 0,72. To fat. If I start the car after 30 min or so it starts perfect. The pressure is 7 bar (ca 102 lbf/in2). I have a rather new Bosch pump and 10 kvm cable to that so thats is not the problem. The injectors gives all a very nice spray when the engine is running. What to do??? Quote Link to post Share on other sites
John L Posted August 1, 2020 Report Share Posted August 1, 2020 Is the choke cable opening MU enough? Could be the little injector seals be leaking allowing the fuel to leak out, or the non return valves in the adaptors at the MU allowing fuel to drain back. Do you let the pump run for a while before cranking? Sometimes helps. What's the pressure at the MU when cranking? John Quote Link to post Share on other sites
nylen Posted August 1, 2020 Author Report Share Posted August 1, 2020 Thanks for the answer, Yes. The choke cable is opening the MU enough. It is not the injector seals but perhaps the non return valve. But the non return valve was new when the MU was returned from PDI. It doesn´t help to run the pump a long time. The pressure at the MU when cranking is 7 bar. Bengt Quote Link to post Share on other sites
nylen Posted August 1, 2020 Author Report Share Posted August 1, 2020 I measured the pressure once more. When I crank the engine the pressure "goes" between 6,7 to 7,0 bar. When the engine started the pressure is steady 7,0 bar. Quote Link to post Share on other sites
John L Posted August 1, 2020 Report Share Posted August 1, 2020 I think 7 bar is a bit low, it can go up to 7,5 bar running. I mean the little o ring in the tip of the injector, if it leaks it will let the fuel run back into the mu, so the engine has to turn over a while until the pipe fills up again. which injector lines are you using the black thin tubes? Also one of the unions could be leaking a bit of air, but not enough to leak fuel strangely enough. I have taken the non return valve rubber sealing washer out and turned them over, the seats in the union are not well machined, I did all except 2 and 5, I just hooked out the spring turned the rubber over and has been better for a while. Mine doesn't start on all cylinders if left for say a week or two, I know it would be nice, but once its been running it will fire up on all 6. John Quote Link to post Share on other sites
nylen Posted August 4, 2020 Author Report Share Posted August 4, 2020 Thanks John. I will follow your advice. Quote Link to post Share on other sites
jerrytr5 Posted August 5, 2020 Report Share Posted August 5, 2020 On 8/1/2020 at 10:00 AM, nylen said: When the car has been i garage for a week or more I have to crank the engine up to 30 sec before It will start on some of the cylinders. After a minute or so it revs perfect on all cylinders. Isn't that fairly normal ? Not something I'd worry about. Jerry Quote Link to post Share on other sites
DOYLEY Posted August 6, 2020 Report Share Posted August 6, 2020 Hi Nylen, Started my TR5, this afternoon, been in the garage for 5 days. Choke half out, a tickle with the right foot, and need to crank for about 10 seconds. (I always let the pump do its job for about 5 seconds before I attempt to start). Coughs a bit for first few hundred yards when I put the choke in fully. (single cable connection) Once warmed up, runs well.... On return home checked the 6 PI pipes with my hands all pumping fuel. Fuel pump cool to the touch mounted under wheel arch. I have just had the cylinder head converted to unleaded, and switched to Shell V-Power. - 99RON Hope this helps Regards Doyley Quote Link to post Share on other sites
Harbottle Posted August 10, 2020 Report Share Posted August 10, 2020 Hello Nylen I agree with Jerry and Doyley's comments. I turn mine on and leave it 20 secs or so and the choke half out, start it up with a bit of right foot and it kicks into life on 5 cylinders and the 6 th joins in. Paul Quote Link to post Share on other sites
rvwp Posted November 11, 2020 Report Share Posted November 11, 2020 Hi Guys I have had this same problem since foolishly swapping out my Ken Mills rebuilt Metering Unit on my 6 for a NF unit. With the KM unit the car started easily even after quite a long winter layup. An old friend of mine who worked for a Triumph sales garage back in the day said that starting new PI cars was never an issue when left for months waiting a sell. I recently came across a Lucas service memo, which I can't find now, which referred to this problem and recommended that the non-return valves in the MU could be the problem as they consist of a spring loaded metal disc and suggested a leak test by removing and filling the attached fuel line with fuel and see if it leaks over time. As these non return valves are not available new now, one wonders how well they are checked when the MU's are rebuilt, they will be 50 + years old. They can be taken apart and possible cleaned, surfaces lapped, quite a fiddly job, but are they? Rich Quote Link to post Share on other sites
John L Posted November 11, 2020 Report Share Posted November 11, 2020 The non return valves are available, I would go to KMI first choise, Moss doesnt have any, but Rimmers do, will need to the other 2 banjo ones as well, https://rimmerbros.com/Item--i-RR1297 https://rimmerbros.com/Item--i-518630 Rimmers have a discount of 12.5 for over £100 less vat. John Quote Link to post Share on other sites
rvwp Posted November 11, 2020 Report Share Posted November 11, 2020 Ah, I did not realize that. However a bit pricey to change all the valves in the hope that it might reduce possible drain down over time which may be the cause of bad starting. It would be interesting to know if anybody has fitted a 'new' Rimmer or KMI metering unit, which presumably has new valves fitted, and does not have the typical 5/6 starting problem after layup for a couple of weeks or more. I guess most go for the cheaper refurbished option that may not have new valves fitted? Rich Quote Link to post Share on other sites
Mick Forey Posted November 12, 2020 Report Share Posted November 12, 2020 Before looking at the non-return valves I would test the injectors as they are notoriously bad at sealing and far easier to get at. I assume a hot-soaked engine can evaporate the fuel in the lines up through the injectors. In my experience only a small amount of air in the injector lines takes ages to clear before pressure is built up enough to get a fine spray. Mick Quote Link to post Share on other sites
Waldi Posted November 12, 2020 Report Share Posted November 12, 2020 My MU and injectors were reconditioned, this week it started after 2 short starts and ran on 6 cyl. immediately. Waldi Quote Link to post Share on other sites
Peter V W Posted November 13, 2020 Report Share Posted November 13, 2020 Are 125bhp and 150bhp metering units the same, but just set up differently? Peter Quote Link to post Share on other sites
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