Slower starting

[John McCormack]

2 minutes ago, TR NIALL said:

I’ve never have to use full enrichment mine will start by just slightly cracking open the Choke with a bit of enrichment from the MU,I turn the Ignition on for between 30/45 seconds pull the Choke slightly and flick the Starter it normally fires and I push back in Choke back in immediately and then control tickover with the loud pedal.  

That is what mine was doing. More choke but essentially the same.

Even now when it fires I push the choke back in and within a few seconds she will idle OK, a bit slow around 500-550 until warm when it idles at 750-800.

It just needs a good few cranks now, between 3 and 5 of 3 or so seconds each, before starting. 

[TR Rob]

Back in the early 70’s I owned a TR6, I bought it cheaply as the petrol injection was poorly set up. At the time I lived in Cheshire and a local diesel tractor specialist rebuilt and retuned the system for me. It ran perfectly . I had just left university and my first job meant I was seconded to a factory in Grimsby, it was much colder in the winter than in Cheshire and my TR6 would not start on the “Cheshire” settings. Overcame this by using a can of Bradex Diesel Start, quick spray into the air cleaner and away she went. 
I remember the engine would rev independently of the throttle, depending on how much of a squirt I had given it.

Probably not what you would want to do to your pride and joy today, but in those days it was just a car, and disappointingly rusted away before your eyes. 
 

As an aside prior to the tune up it was doing about 10 mpg and the fuel gauge went down like the minute hand on a clock, after it did about 28 mpg……those were the days !!!

Edited January 5 by TR Rob
Typo

[John McCormack]

This morning I gave her full choke, didn't touch the accelerator pedal and let the pump run for 30-40 seconds before cranking. Started immediately.

It is only once but maybe it was my starting technique that was the problem.

[JohnC]

Hi @John McCormack,

I've experienced a very similar/identical problem - cranking time increasing - a couple of times. Even though you may have found a work-around for your starting problem, these may provide food for thought.

The first was a tired battery which led to low fuel pressure when cranking. I diagnosed that with a pressure gauge in the fuel line. Interestingly, letting the pump run for a little while before starting somewhat alleviated the problem. The cranking speed was not noticeably slower BTW. Like you, I have a Bosch pump. At the time, it was fed by the old wiring, which I suspect magnified the problem. Since then I have upgraded to nice fat wires, using the original ones to switch a relay.

The second time was leaky injectors. The symptom was that the car took a *lot* more cranking after being left for only a few days. I diagnosed the problem by replacing the black injector lines with translucent white ones. I could see the size of the air bubble increasing daily. Not equally across all injectors BTW. I tested the injectors using an airline and a bucket of water, and could see bubbles well before the 50psi point. Crude, I know (air vs petrol). Changing the O rings didn't fix the problem so I sent the injectors off to Peter Bower for re-seating. Problem solved (pity he's no longer in business).

Incidentally, even with reconditioned injectors, there is always a small air bubble in each injector line after the car has sat for a while. So I figure that the poppet valve isn't a perfect seal, and that when the car is hot a bit of fuel vapour makes its way out, being replaced by air. And before anyone jumps in, yes, I do know all the non-return valves are working fine. I had them tested when I got the injectors reconditioned.

Hope this helps,
JC

[John McCormack]

On 1/6/2024 at 10:02 AM, John McCormack said:

This morning I gave her full choke, didn't touch the accelerator pedal and let the pump run for 30-40 seconds before cranking. Started immediately.

It is only once but maybe it was my starting technique that was the problem.

Again today, full choke and let the pump run for 30+ seconds and it started immediately. I didn't start yesterday so it was 48 hours between starts.

It might be a answer to other PI owners who experience starting problems. 

[Mike C]

That's like mine, but you might have to crank it over a bit more if you leave it for more than a week or two between starts-just like mine.

[TRier]

It could be the injection system losing prime, as was pointed out leaky injectors but also ineffective NRVs will cause the system to lose prime downstream of the FMU and consequently require more cranking to prime again. With the exception of 5 & 6 they are just rubber discs in the output ports of the FMU, worth a look to check that the haven’t cut “seats” into the rubber discs.

[John McCormack]

Has anybody used Accuspark AC9C plugs? They are recommended for the TR6 and I have a set of new ones. Worth fitting?

[roy53]

I have found that when a new battery fitted the problem goes so as Neil mentioned power seems to be relevant. Also cleaning the earth connections to both engine and bodywork.This worked on a couple of cars for me. Also I ran after solving this a stronger cable to the pump . A forum bit of advice

 

Roy