PI problem

[nylen]

Hi,

 

I have a TR5 since many years with type of Bosch pump (From PDI). The installation is made as attached figure. I works well but I have one problem and this has been the case in many years. It is perhaps time to do anything about it. When I am starting the car after one night the engine starts very well. If the car has been in the garage for some weeks I have to rev the engine a long time before I got fuel so the engine starts.

I have a lot of electric power to the pump (6 kvmm copper cable) and a good battery so this is not the problem. The MU is rather new. The MU was recondition by PID a few years ago but the starting problem is the same as before it was reconditioned.  I have friends with TR6 PI and TR5 with the same problem.

Is it possible insert a return valve in some of the pipes. If so, where?? Some other good ideas?

[Waldi]

Hi Nylen,
my TR6-PI requires 3 or 4 intermittent cranks as well when it stood for a couple of weeks, months.

I think the combined leakages (back to tank) of PRV, MU and pump cause this. The injectors are not a perfect seal either, so some air may be sucked in since this is the highest point.

A Bosch pump normally has an NRV in the discharge connection, mine was new in 2019.

I do not worry about it, it is a constant behaviour, and I have told myself it is design related so often, this is my truth:)

Waldi

[Mike C]

Try switching the ignition on and let the Bosch pump run for 30 seconds or so to fill up the system before you crank. You can generally hear the pump change note.

This will reduce the cranking required after a long period of inactivity but it still won't ensure instantaneous firing. I've never seen a PI modification that will make a TR fire up like a modern car.

 

[nylen]

Hi Mike!

I have of course done that every time. 

[astontr6]

23 hours ago, nylen said:

Hi,

 

I have a TR5 since many years with type of Bosch pump (From PDI). The installation is made as attached figure. I works well but I have one problem and this has been the case in many years. It is perhaps time to do anything about it. When I am starting the car after one night the engine starts very well. If the car has been in the garage for some weeks I have to rev the engine a long time before I got fuel so the engine starts.

I have a lot of electric power to the pump (6 kvmm copper cable) and a good battery so this is not the problem. The MU is rather new. The MU was recondition by PID a few years ago but the starting problem is the same as before it was reconditioned.  I have friends with TR6 PI and TR5 with the same problem.

Is it possible insert a return valve in some of the pipes. If so, where?? Some other good ideas?

Looking at your schematic drawing! What bore size is the pipe work from tank to pump? Also can you show the lay out of your installation with a photo. I was told years ago by Martins injection who developed the Bosch replacement with KMI that the Bosch filter s/b before the pump. The reason that was given that this guards against air locks I never understood how this works, as petrol has a lot of absorbed air in it which freely comes out. The old CAV filter had a bleed screw to let the air out.

Bruce.

[nylen]

I have a big bore outlet from the tank bought from PDI.

[Harbottle]

Hi Nylen, I have had a my TR5 for 20 years now with a new Bosch pump which replaced the old Bosch pump and filter and metering unit reconditioned. It still does as yours, I do what Waldi and Mike said and just live with it, when it does not start at all is the time to worry.

Paul

[nylen]

Thanks for all your answers. I have never used a PI-car with Lucas originally system. I just wonder. If that system behaved the same way all buyers of new cars 1969-75 must have been angry! If the Lucas originally system was better it must be a way to fix a Bosch system too.

[john.r.davies]

4 hours ago, nylen said:

I have a big bore outlet from the tank bought from PDI.

Nylen,

Your whole fuel circuit isn't obvious to me from the photo, but is that pipe along the bottom of the tank to the outlet the return from the PRV?   If so, and when  you are idling/going slowly, with low fuel consumption, that returned fuel will recirculate.    The Bosch does heat it up, so passing the fuel through the pump repeatedly might mean that the fuel delivered to the M/u and injectors was hot!   But fuel evaporation in the lines doesn't seem to be your problem!

Mine does the same, prolonged churning before a start after 'resting'.   I attribute it to leak-back from the injectors, which may indicate that their needles are worn, as some KwikStart sprayed into the air filter    get its going quicker, and even so, it will start on 3-4 cylinders until the others catch up.

Mind you, I take a while to get going in the morning!

John

[Rob Y]

Hi Nylen 

I had similar problems to you on my tr6 with Bosch pump etc.

I replaced all the O Rings on the injectors and the problem has gone away (for me). It’s an easy and very cheap job to do.

Now my car starts pretty much first time even in the winter when it’s cold and it’s been standing for weeks.

Might be worth a try.

Cheers, Rob.

[nylen]

Thanks Rob. I will try that.

 

[nylen]

Rob,

You mean the O ring inside in the injector?

[Rob Y]

I replaced both O rings. The one inside the injector and the one that seals the injector to the throttle body. Might as well do both while you’re at it.

When I did this the old O rings were square in section so it was obvious they needed doing. Good to get Viton when you do this too for better resistance to ethanol.

[astontr6]

7 hours ago, nylen said:

I have a big bore outlet from the tank bought from PDI.

Hi Nylen!

Thanks for you response.

A Bosch Pump to work satisfactory needs a minimum of 2.6 liters per min preferably 5 liters per min at the pump. It would be interesting if you checked this to see if your pipework meets this spec. These figures were give to to me by Bosch Engineering some 40+ years ago! The pipework  looks a bit restrictive on the blue filter to pump . The original Lucas/CAV pipework to pump only gives 1.7 LPM hence often gave a very noisy Bosch Pump. I use 10m/m bore fuel line,

Bruce.

[JohnC]

You will get air bubbles in the injector lines if there is any issue with the injector poppet valve, the internal 'O' ring, or the non-return valve. I fitted translucent white injector lines a while ago and it really shows up if one or more line is getting air bubbles. My experience is that a small bubble (~2cm long) is pretty much as small as you'll get it, possibly because it's caused by air being drawn in as the fuel cools (?). That size bubble clears with no hesitation on starting. Anything in the 5cm range or larger causes a delay in that cylinder catching. In the case of my car the poppet valves all needed re-seating. The 'O' rings made a difference but didn't fix the problem entirely.

JC

[michaelfinnis]

2 hours ago, JohnC said:

You will get air bubbles in the injector lines if there is any issue with the injector poppet valve, the internal 'O' ring, or the non-return valve. I fitted translucent white injector lines a while ago and it really shows up if one or more line is getting air bubbles. My experience is that a small bubble (~2cm long) is pretty much as small as you'll get it, possibly because it's caused by air being drawn in as the fuel cools (?). That size bubble clears with no hesitation on starting. Anything in the 5cm range or larger causes a delay in that cylinder catching. In the case of my car the poppet valves all needed re-seating. The 'O' rings made a difference but didn't fix the problem entirely.

JC

John, what do you mean by reseating the poppet valves? I assume you mean pulling the tip and releasing, but is that any different from what they do when running?

Mike.

[Gordon Bayley]

I had the same problem with starting , I changed all 6 injectors now it starts straight away.

[roy53]

I have been dealing with 2 TR6s and my 5 which all are suffering troubled starting after a rest even overnight.

So been following these type of posts. Both 6s have new metering and injectors.

Once been started they are all immediate starters.

What i have found for the past 4 days on initial start i have connected a battery booster and got first time starting.

So am thinking that a slightly down battery overnight is my problem. When it gets a bit of charge when running it's fine for the rest of the day.

Roy

[ntc]

29 minutes ago, roy53 said:

I have been dealing with 2 TR6s and my 5 which all are suffering troubled starting after a rest even overnight.

So been following these type of posts. Both 6s have new metering and injectors.

Once been started they are all immediate starters.

What i have found for the past 4 days on initial start i have connected a battery booster and got first time starting.

So am thinking that a slightly down battery overnight is my problem. When it gets a bit of charge when running it's fine for the rest of the day.

Roy

You presume correctly Roy that  is what I have found out myself before 

[Tom B]

On 5/22/2023 at 10:58 AM, michaelfinnis said:

John, what do you mean by reseating the poppet valves? I assume you mean pulling the tip and releasing, but is that any different from what they do when running?

Mike.

I think John means that the valves on the poppet valve are much like the valves in the cylinder head. The injectors can be disassembled and, using some grinding paste the seats can be re-cut. It also helps to set the opening pressure of the valves to ~50psi. If you search the forums there are ways of doing this (I posted something myself). It is not difficult but requires a little patience and for goodness sake don't lose the snap ring! (I have been unable to find a source for these) A simple test, though, is to run the engine, stop it and take the injectors out and see if they are leaking. A well tuned nose will help you with this.

[harrytr5]

On 5/21/2023 at 12:22 PM, nylen said:

I have a big bore outlet from the tank bought from PDI.

Hi Nylen,

Never seen that arrangement of pipe work and two feeds. Those 90 degree unions look a bit restrictive!. Favourite mod is to fit the pump and filter to the outside in the cooler air. I always fit a fuel tap for ease of servicing. My Tr5 has been on EFi since 2010 as you know but the principal is the same.

[Paul Hill]

Since I changed my tank which as the Bigger outlet I have had zero problems. Never seen that setup regards the bottom piping under the tank. Here is mine

[kiwican]

5 hours ago, Paul Hill said:

Since I changed my tank which as the Bigger outlet I have had zero problems. Never seen that setup regards the bottom piping under the tank. Here is mine

Does the spare tyre still fit with the pump and filter mounted where it is? Mine is bolted to the original CAV mounting and am not sure if my spare would fit with where your set up is placed.

Simon

Edited May 27, 2023 by kiwican

[Paul Hill]

Yup I still get the spare in, there is about 1 1/2” clearance.

[JohnC]

On 5/27/2023 at 5:28 AM, Tom B said:

I think John means that the valves on the poppet valve are much like the valves in the cylinder head. The injectors can be disassembled and, using some grinding paste the seats can be re-cut. It also helps to set the opening pressure of the valves to ~50psi. If you search the forums there are ways of doing this (I posted something myself). It is not difficult but requires a little patience and for goodness sake don't lose the snap ring! (I have been unable to find a source for these) A simple test, though, is to run the engine, stop it and take the injectors out and see if they are leaking. A well tuned nose will help you with this.

Exactly so. But, as others have already posted, a battery in good condition is also very important to immediate starting.

John