S1 hot start problem
Discussion
I’m trying to solve the hot start issue on my 2.8 S1, it will start after cranking for 5-10 seconds with the throttle open but will take a little while to come back onto 6 cylinders.
I checked the pressure between the metering head and with WUR yesterday. System pressure is 75psi and control pressure rises as it should to 52psi when hot, and holds for long enough when cooling down with the engine off.
The only two problems I found are with the vacuum feed disconnected to the WUR when the engine is hot and running the fuel control pressure goes up 8 psi, i understand it should come down to richen the mixture under high load so I have a problem with the WUR.
Also the sensor plate was too low so I’ve raised it inline the the bottom of the cone and reset the CO.
What I don’t understand is when the metering head is holding pressure with the engine switched off, if you disconnect an injector fuel line and release the initial fuel pressure there is no fuel flow unless you lift the sensor plate slightly.
Surely to stop the injector lines vapour locking there should still be pressure coming from the metering head?
I checked the pressure between the metering head and with WUR yesterday. System pressure is 75psi and control pressure rises as it should to 52psi when hot, and holds for long enough when cooling down with the engine off.
The only two problems I found are with the vacuum feed disconnected to the WUR when the engine is hot and running the fuel control pressure goes up 8 psi, i understand it should come down to richen the mixture under high load so I have a problem with the WUR.
Also the sensor plate was too low so I’ve raised it inline the the bottom of the cone and reset the CO.
What I don’t understand is when the metering head is holding pressure with the engine switched off, if you disconnect an injector fuel line and release the initial fuel pressure there is no fuel flow unless you lift the sensor plate slightly.
Surely to stop the injector lines vapour locking there should still be pressure coming from the metering head?
Edited by AlfaSpider on Monday 29th July 13:11
Edited by AlfaSpider on Monday 29th July 13:12
NOT an easy job to fit EFi to a 2.8, electrical issues as well.
The 2.8 is indirect injection, all the injectors are on all the time the engine is running, when the air meter drops to datum setting it should close off ALL the fuel to the injectors. They do not vapour lock as the pipe is not 'closed' at the injection end.
You have reset the air meter height, that will alter the point at which fuel starts to be released to the injectors, it will also alter the initial mixture setting. The meter plate should be perfectly in the centre of the air meter orifice, if the plate has been moved is that still correct. The plate should be slightly below the start of the taper section, in the plain tube section, typically about 1mm down. When the engine starts to exert vacuum on the plate, it has to rise slightly before air is admitted to the throttle, as it first starts to rise the fuel should start to be released BEFORE the air meter allows air in. During that period the auxiliary air valve is providing the air for the engine to start. If the plate is a touch too high the initial mixture at very low throttle will be weak. Setting the CO2 when the engine is at 1000rpm or less should be impossible if the initial opening mixture is wrong. You might get it right at 1500rpm but it will be wrong when the plate drops.
How did you reset the plate? Did you adjust the spring pressure to do it? I have to say it can be a bugger to get it right again once the initial opening air to fuel ratio has changed.
I would not have expected that to be the cause of hot start problems. Does it start OK when cold? If so I doubt if the air meter is the problem.
The 2.8 is indirect injection, all the injectors are on all the time the engine is running, when the air meter drops to datum setting it should close off ALL the fuel to the injectors. They do not vapour lock as the pipe is not 'closed' at the injection end.
You have reset the air meter height, that will alter the point at which fuel starts to be released to the injectors, it will also alter the initial mixture setting. The meter plate should be perfectly in the centre of the air meter orifice, if the plate has been moved is that still correct. The plate should be slightly below the start of the taper section, in the plain tube section, typically about 1mm down. When the engine starts to exert vacuum on the plate, it has to rise slightly before air is admitted to the throttle, as it first starts to rise the fuel should start to be released BEFORE the air meter allows air in. During that period the auxiliary air valve is providing the air for the engine to start. If the plate is a touch too high the initial mixture at very low throttle will be weak. Setting the CO2 when the engine is at 1000rpm or less should be impossible if the initial opening mixture is wrong. You might get it right at 1500rpm but it will be wrong when the plate drops.
How did you reset the plate? Did you adjust the spring pressure to do it? I have to say it can be a bugger to get it right again once the initial opening air to fuel ratio has changed.
I would not have expected that to be the cause of hot start problems. Does it start OK when cold? If so I doubt if the air meter is the problem.
greymrj said:
NOT an easy job to fit EFi to a 2.8, electrical issues as well.
The 2.8 is indirect injection, all the injectors are on all the time the engine is running, when the air meter drops to datum setting it should close off ALL the fuel to the injectors. They do not vapour lock as the pipe is not 'closed' at the injection end.
You have reset the air meter height, that will alter the point at which fuel starts to be released to the injectors, it will also alter the initial mixture setting. The meter plate should be perfectly in the centre of the air meter orifice, if the plate has been moved is that still correct. The plate should be slightly below the start of the taper section, in the plain tube section, typically about 1mm down. When the engine starts to exert vacuum on the plate, it has to rise slightly before air is admitted to the throttle, as it first starts to rise the fuel should start to be released BEFORE the air meter allows air in. During that period the auxiliary air valve is providing the air for the engine to start. If the plate is a touch too high the initial mixture at very low throttle will be weak. Setting the CO2 when the engine is at 1000rpm or less should be impossible if the initial opening mixture is wrong. You might get it right at 1500rpm but it will be wrong when the plate drops.
How did you reset the plate? Did you adjust the spring pressure to do it? I have to say it can be a bugger to get it right again once the initial opening air to fuel ratio has changed.
I would not have expected that to be the cause of hot start problems. Does it start OK when cold? If so I doubt if the air meter is the problem.
I have reset the meter plate to just below the bottom of the cone furthest from the metering head, before I adjusted it i would guess it was about 1.5-2mm below. The mixture screw was still very sensitive after this adjustment but perhaps it is now a touch too high. The 2.8 is indirect injection, all the injectors are on all the time the engine is running, when the air meter drops to datum setting it should close off ALL the fuel to the injectors. They do not vapour lock as the pipe is not 'closed' at the injection end.
You have reset the air meter height, that will alter the point at which fuel starts to be released to the injectors, it will also alter the initial mixture setting. The meter plate should be perfectly in the centre of the air meter orifice, if the plate has been moved is that still correct. The plate should be slightly below the start of the taper section, in the plain tube section, typically about 1mm down. When the engine starts to exert vacuum on the plate, it has to rise slightly before air is admitted to the throttle, as it first starts to rise the fuel should start to be released BEFORE the air meter allows air in. During that period the auxiliary air valve is providing the air for the engine to start. If the plate is a touch too high the initial mixture at very low throttle will be weak. Setting the CO2 when the engine is at 1000rpm or less should be impossible if the initial opening mixture is wrong. You might get it right at 1500rpm but it will be wrong when the plate drops.
How did you reset the plate? Did you adjust the spring pressure to do it? I have to say it can be a bugger to get it right again once the initial opening air to fuel ratio has changed.
I would not have expected that to be the cause of hot start problems. Does it start OK when cold? If so I doubt if the air meter is the problem.
Unrelated to the hot start issue taking the WUR valve apart I have found the piston / diaphragm was clogged with congealed coolant and could not drop when vacuum reduced to lower the control pressure. The car has maybe been holding back slightly at high rpm so hopefully this will fix it.
With regards to the starting issue it’s always when hot, but also cold unless I leave the car for about 48hrs then it’s ok again.
I was going to check the injectors were holding pressure and not leaking as I understand they shouldn’t spray fuel until about 30psi?
I see what you were saying about the injectors not being ‘closed’ but also I suppose however long I left it before restarting if the injector lines are not holding pressure this shouldn’t make a difference.
I have yet to check the single point injector into the plenum but I’m not sure this would cause these symptoms.
I have yet to check the single point injector into the plenum but I’m not sure this would cause these symptoms.
|https://thumbsnap.com/HZil7RTz[/url]In reply to...
NOT an easy job to fit EFi to a 2.8, electrical issues as well.
IMHO, on a bespoke car such as the S, there aren't many involved jobs that ARE easy. The conversion to efi on a 2.8 unit IS straightforward, I know, I have done it.
Yes, there is electrical work to do, and again that is involved.
But as always, as a caveat, you shouldn't take on any work that you're not equipped or skilled to carryout.
ECUs such as Emerald will come with comprehensive wiring instructions, and if you talk to the guys at Emerald, they are most happy to guide you through your installation. The few ecu peripheral sensors required, are common place, and stock reliable.
Oh, yes, its my 2.8efi hardware kit that's currently for sale on FB.
And the 2nd photo is my 3.0 'stroker' engine (built and re engineered 1983 2.8 carb unit).
Note.. I have only named Emerald ecu as that's my personal preference, but there are many fine ECU's available.
NOT an easy job to fit EFi to a 2.8, electrical issues as well.
IMHO, on a bespoke car such as the S, there aren't many involved jobs that ARE easy. The conversion to efi on a 2.8 unit IS straightforward, I know, I have done it.
Yes, there is electrical work to do, and again that is involved.
But as always, as a caveat, you shouldn't take on any work that you're not equipped or skilled to carryout.
ECUs such as Emerald will come with comprehensive wiring instructions, and if you talk to the guys at Emerald, they are most happy to guide you through your installation. The few ecu peripheral sensors required, are common place, and stock reliable.
Oh, yes, its my 2.8efi hardware kit that's currently for sale on FB.
And the 2nd photo is my 3.0 'stroker' engine (built and re engineered 1983 2.8 carb unit).
Note.. I have only named Emerald ecu as that's my personal preference, but there are many fine ECU's available.
Sorry, but once you have had the warm up regulator apart it is almost certain to need re-calibration which really needs special equipment. KMI are the experts. It is possible to get the car working with a faulty regulator, but what you then have are a series of wrong adjustments compensating, and it will never be right. Faulty regulators are common after the kind of period these have been operating. I had one which held fuel pressure fine, but the level it held it at varied, so one day it was right, the next day it wasnt!
Two possible faults to look at;
The symptom that it faults to hot start and sometimes fails to cold start until time has passed does possibly indicate the auxiliary air valve is sticking. That wouldn't be surprising after all this time. It is simple disc with a hole in it which turns according to temperature.
The issue with the seventh injector is that it is operated by a relay which is supposed to respond to heat and close it off. They are known for not responding properly and particularly for not shutting off when hot so a hot start is well over rich. For a time I had to disconnect mine once the car was running and only reconnect when cold. Now I have a switch in the cabin to ensure it is switched off after starting.
There is one little issue outside the K Jet which can cause hot start problems. The spark accentuator unit starts to break down with age and becomes sensitive to heat, when hot it doesnt work properly. Spark becomes too weak to start the engine but runs adequately when started.
Two possible faults to look at;
The symptom that it faults to hot start and sometimes fails to cold start until time has passed does possibly indicate the auxiliary air valve is sticking. That wouldn't be surprising after all this time. It is simple disc with a hole in it which turns according to temperature.
The issue with the seventh injector is that it is operated by a relay which is supposed to respond to heat and close it off. They are known for not responding properly and particularly for not shutting off when hot so a hot start is well over rich. For a time I had to disconnect mine once the car was running and only reconnect when cold. Now I have a switch in the cabin to ensure it is switched off after starting.
There is one little issue outside the K Jet which can cause hot start problems. The spark accentuator unit starts to break down with age and becomes sensitive to heat, when hot it doesnt work properly. Spark becomes too weak to start the engine but runs adequately when started.
Picking up in reference to the spark accentuator, commonly referred to as the Duraspark Ignition Amplifier. (Sorry, unless you're referring to the ignition coil)
If the 2.8 Tvr S uses the 6 wire version of this, then it is most likely that the starter motor has an extra thin wire. During cranking, this sends a signal to the amp, which in turn introduces a fixed time delay on the output to the ignition coil. That delay is of course, a fixed amount of timing retard. Which makes cranking easier. As soon as cranking ceases, the timing is back to normal.
The point I'm making is, that if either the starter motor cranking signal remains active, or the Duraspark unit goes faulty in this manner, your timing will be out (retarded) during normal running... Not a good thing !!
If its a faulty starter output signal, simply pull the wire off, you won't notice any difference. If its the Duraspark, it will need replacing.
Carrying a known good spare Duraspark unit with you, seems to be a good idea on 30yr+ old cars.
Some time ago, I did rig up a prototype replacement amplifier unit, using another manufacturers ignition module (from a much later car), thus being still readily available, unlike the seemingly and increasingly rare genuine Ford Duraspark unit.
Must see if I can find it out...
Oh, if you're considering fitting nitrous oxide to a 2.8. Manually switching the ignition to a retard position is a useful feature ... Nar, dont do it 👎👎
TerryB
If the 2.8 Tvr S uses the 6 wire version of this, then it is most likely that the starter motor has an extra thin wire. During cranking, this sends a signal to the amp, which in turn introduces a fixed time delay on the output to the ignition coil. That delay is of course, a fixed amount of timing retard. Which makes cranking easier. As soon as cranking ceases, the timing is back to normal.
The point I'm making is, that if either the starter motor cranking signal remains active, or the Duraspark unit goes faulty in this manner, your timing will be out (retarded) during normal running... Not a good thing !!
If its a faulty starter output signal, simply pull the wire off, you won't notice any difference. If its the Duraspark, it will need replacing.
Carrying a known good spare Duraspark unit with you, seems to be a good idea on 30yr+ old cars.
Some time ago, I did rig up a prototype replacement amplifier unit, using another manufacturers ignition module (from a much later car), thus being still readily available, unlike the seemingly and increasingly rare genuine Ford Duraspark unit.
Must see if I can find it out...
Oh, if you're considering fitting nitrous oxide to a 2.8. Manually switching the ignition to a retard position is a useful feature ... Nar, dont do it 👎👎
TerryB
Edited by Blue 30 on Thursday 1st August 10:42
Thank you for all the helpful advice. Regarding the WUR valve I will get it check by kmi to make sure it’s operating as it should, I know there was an issue as the enrichment function was in fact leaning it out.
I did consider in the past putting lambda bosses in the exhaust downpipes to use an afr meter, something I never got round to and seems a tad excessive.
I’ve got the inlet manifold off cleaning everything as it’s a bit grotty anyway, I’ll be sure to check the auxiliary air valve and 7th injector function.
I do wonder whether it could be ignition module related as very occasionally it takes longer to clear the misfire, switching the engine off and back on again sorts this out.
I think it all just needs checking/ servicing as it’s on 97k!
I did consider in the past putting lambda bosses in the exhaust downpipes to use an afr meter, something I never got round to and seems a tad excessive.
I’ve got the inlet manifold off cleaning everything as it’s a bit grotty anyway, I’ll be sure to check the auxiliary air valve and 7th injector function.
I do wonder whether it could be ignition module related as very occasionally it takes longer to clear the misfire, switching the engine off and back on again sorts this out.
I think it all just needs checking/ servicing as it’s on 97k!
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