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Pinto EFI - Air lock Issue?


FERRINO

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Evening all,

I finally got the engine fired up and running a couple of weekends ago - great milestone! However, when I leave it running for 20 mins or so (or give it some revs under load), it conks out and won't start again.

The only way to get it running again is to crack the connection to the fuel rail - retighten - wipe up the excess. After that it fires up again straight away.

Setup is this:-

Aluminium tank, baffled with swirl pot middle-center. 8mm I/D injection hose from swirl pot to low pressure Sytec filter (it looks uphill in pic but it straight and level). 8mm I/D  injection hose running downhill to Sytec P3017.1 Injection pump. 8mm I/D Injection hose to high pressure Sytec Filter. 8mm I/D injection hose running down tunnel and up onto bog standard Pinto EFI fuel rail. 8mm I/D injection hose from bog standard fuel pressure regulator at end of fuel rail running back down tunnel and into top of fuel tank. Rollover vent valve fitted to fuel tank so it breathes. Pics below :-

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When the engine is running - if you lightly touch the Injection hose where it goes into the fuel rail, it coughs and splutters and nearly conks out.

With that in mind I figured it must be a fuel pressure problem - so bought a cheap gauge set and plumbed it inline to see what pressure I'm getting. According to research, Pinto EFI fuel system runs at approx 2.5 bar. I haven't had the engine running with the gauge on - but priming pressure on the pump looks like approx 2.2 bar which seems close enough taking inaccuracy of the gauge into account etc. 

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I've checked the fuel is returning to the tank - which it is. I've tried running it with the fuel cap off - same issue. Pump is rated at 8.5 bar so the standard fuel pressure reg is obviously working.

When it stops - the only way to get it re-started is to crack the fuel rail connection? This makes me think that somehow I'm getting an air lock in the fuel line onto the rail and cracking it is releasing the trapped air? The thing that's confusing me is the the fact that there is no fuel escaping when running - so how is air getting in and trapped? Also why is it struggling so much with the lightest touch on the inlet hose to the fuel rail if the pressure is about right? I know the hose drops downhill onto the rail - but so does the standard Ford connector (admittedly not as much). But there shouldn't be any air in that hose - or if there was, wouldn't it get forced out of the injectors when they open?

Is there something obvious I'm missing here please peeps? Got loads more jobs to do for IVA in the meantime - but this one one is bugging the hell out of me lol!

Cheers

Tony

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I think an air lock is unlikely if the pump is giving 8.5 bar. That's enough to purge any air and yes it will purge through the injectors easily. You can confirm that the pressure regulator is on the fuel rail outlet and not at the input end? Fascinating (and handy) that the fault is so repeatable.

Then in use for your fuel pressure to fail something goes beyond its weakest point. I suspect the fuel pumps ability to suck is its weakest point. Replace the low pressure pre-pump filter with a cheapo £1 ebay see through plastic one or even temporarily test run without it if your fuel tank is clean enough. My first thought was fuel filter clogging and collapsing and the pump failing to suck through it. Release of hose at rail allows slight back flush to slightly clear the filter. Air (if it enters) enters between LP filter and pump. If it's not the filter then something in the tank blocking the outflow. Other thought was tank vacuum but you say no.

No this doesn't explain why touching the inlet hose is a problem and may not explain why releasing it cures it temporarily. I take it you have examined those joints and the holes are unobstructed.

Would be usefull to know what the fuel pressure gauge reads when the engine stalls.

Edited by Longboarder
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Thanks for the reply Nigel - food for thought certainly. I will def get a cheapo see through filter on order.

I'm still perplexed as to why cracking the fuel rail connection sorts the problem (temporarily) though - that has to be trapped air doesn't it? Low fuel pressure would still be low fuel pressure even after breaking the joint temporarily?

As you say - I've not had the engine running since fitting the pressure gauge so must try and get home early one night this week and get it fired up. Might give a further clue if we can see what's going on with pressures when it's running fine/struggling/conked out etc.

Cheers again

Tony

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Tough one! The touching of the inlet hose - are we saying you're literaly touching it with a finger, no significant pressure, just touching the hose causes it to stall? That sounds more electrical to me; you're adding a ground, or introducing interference into maybe the injectors but... then that doesn't explain why cracking the fuel rail fixes the problem.

Cracking the fuel rail suggest, other than the excellent suggestion from LB above, that maybe some large flake of crud is settling in the rail/injector basket filters and when the throttle is opened it's get drawn into and blocking the injector filters. While pressure is in the system that's getting held in place but cracking the rail is letting the debris pull away from the injector basket and clear it up?

Might be worth pulling the rail and injectors off, flushing out, giving them a gentle upside-down tap to see if any *bleep* comes out of them. But then, this contradicts the "touching the hose" issue! The two don't make any sense to me :-S !! Wow, interesting one...

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Thanks for the reply Dan - it certainly is an interesting one!

With the fuel pipe, It needs to be more than just physical 'contact' to get it splutter - but it's really not a lot of pressure or downwards movement required to get it coughing. Almost a few mm is all it took last time which surprised me that it had any effect at all with 30+ PSI of fluid inside.

That said though - I haven't had it running with the gauge now attached - so it may well be significantly lower than 30 PSI when its running due to some other other issue. Definitely need to make some time this week to annoy the neighbours and get it fired up again. If the gauge still sits at a rock steady 2.2 psi or above, then as you say - pulling it apart to see what's going on in the rail will have to be the next step.

Cheers

Tony

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Thats pretty much the same as my setup, swirl pot in tank(but on left side), pump prefilter, high pressue filter (near engine), return to tank but directed to pot to help avoid fuel starvation when low(pot on left?).

If you touch the hose and it splutters, could be a hose issue, changing the hose should be quick and cheap.

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Thanks Jez - that's good to know it's not something silly with the basic setup if you are running almost the same without issue.

Unfortunately as you can see in the pic below - I stupidly ran the Injection hose solidly from the back of the car to the front via the tunnel and all the way back down the tunnel again. It's the properly marked SAE J30 R9 hose, but I'm hoping it won't need replacing for a couple of years at least as I'd have to rip all the tunnel panelling out to get at it.:-

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I've checked the lines all along the route to and from the engine and can't see any obvious point where it's bent too tightly or constricted anywhere.

I've got a spare EFI rail with the bog standard Ford fuel line and rail fitting still attached - which I also checked. The hard black plastic fuel line Ford used is way smaller than 8mm I/D (less than 5 I would say looking at it) so it shouldn't really be flow rate issue?

Cheers

Tony

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  • 1 month later...

Evening all, Well 39 days later (due to holidays/weddings/general life etc) I finally got time yesterday to fire her up again - first time since fitting the inline gauge.

Apart from fitting the gauge, the only other thing I've done is to put another 5 litres of juice in the tank (maybe I shouldn't have just for continuity sake)?

It did it's usual and wouldn't fire even after several 'primes' - totally as expected. I then cracked the fuel rail and let the pressure drop before retightening. After that, fired up first turn of the key - again totally as expected given previous performances. Pressure remained constant on the gauge at approx 2.5 Bar with engine running and revving up/down and sitting at tickover. This time though, when moving the hose to the fuel rail around, no drop in revs and no coughing/spluttering? Weird? 

Let it run for a while and as it got up to 3/4 temp, tickover was getting very low and needed the throttle opening a little to keep it running which it didn't do before. Struggling quite badly with tickover (sounded way too low). Couldn't see what rpm it was as gauge is not working at the mo. Put it back in the garage and switched it off.

Left it 2 hours and went back in to do a test start (expecting the usual no-start situation and having to crack the rail etc). Pressure had dropped to just over 1 Bar on gauge. Primed it on the key and to my total surprise it fired up straight away?! Weird?

Switched off and left it overnight. Went back in at lunchtime today. 0 Bar on the gauge - surely it won't start now. Primed on ignition and Bang up it went no problem?? Tried again 3 hours later - fired up straight away again. Fired up again every time I tried when hot and also several times when left to cool right down.

Now - I can't quite believe I'm complaining about a a car firing up every time you turn the key lol, but I like a fault to remain until you definitively find the culprit.

Logic would say that the addition of 5 litres more fuel is what has done it and I'd tend to agree at this point pointing to 'supply to pump' area that needs looking at. However - it's the new issue of the crappy running once getting up to temp that is concerning me now? It ran nicely before and now only ticks over nicely when cold. Popped a plug out to check and looks a little black/oily so maybe 'choke enrichment' is staying on now?

Apologies for the essay - but this car is driving me nuts at the mo :)

Cheers

Tony

 

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