Fuel starvation or something else?

[TR5tar]

A couple of months back I mentioned experiencing a loss of power going over a bump in my TR5 PI - http://www.tr-register.co.uk/forums/index.php?/topic/48807-power-loss-over-bumpos/?hl=bumpos

 

However, after that one occasion all seemed fine, so I didn't investigate it further. Yesterday, I decided to go for a nice long run in the chilly weather and all was well freezing my A... off with the top down for the first 10 miles or so, but then coming off a roundabout with the clutch dipped to change gear the engine cut out. I came to a stop and got it started again immediately. My fuel gauge was showing just under half, so I thought I'd fill up just in case the gauge was giving a false reading. I added the usual shot of Millers VSPe Power Plus and then filled it with Shell V-Max as I always do and then set off again. Did another 10 miles or so and after a bit of a 70mph blast found that I lost power again (no acceleration). It actually picked up when I took my foot off the accelerator. I changed down the gears to try to keep it running and put my foot down hard again in second. After a few seconds the power came back (with a blast and a bit of a backfire), but for the next few miles it happened again several times. Then it cleared for a few miles, before starting again.

 

I don't know if this problem is related to the first one I mentioned, or something different. I've not made any changes to the car recently other than topping up the radiator with 50/50 Bluecol antifreeze.

 

I did notice that the car was running quite cold. In the warmer months it usually gets up the halfway point on the temp gauge within a few minutes of running and then stays there when the fan cuts in, but in these colder conditions it's only going up to about 1/4 way.

 

My initial thought is a fuel pump problem, or maybe a blockage. I also wondered about it being a mixture problem, because when it happened it felt similar to what happens if the choke is left out too long.

 

Any ideas?

 

Thanks, Darren

Edited December 15, 2014 by TR5tar

[snowric]

Darren,

 

My car runs in the bottom quarter of the thermostat in this cold weather when driving sat say 40 mph. When I sit in heavy traffic the needle rises again and the fan kicks in as usual.

 

Two possible causes:

 

Electrical fault with the faulty wiring moving as you go over bumps or failing pump etc. so a loose connector, dry joint or dirty/ failing fuse or loose earth.

 

Check the pump output with a pressure gauge connected and tucked under your windscreen wiper, you can see the pressure moving - do you see a sudden drop ?

 

For the pump, check the wiring starting with the earth and checking each connection. I don't know where the standard earthing terminates for the fuel pump, I installed a new one in the boot when I put in a separate feed.

 

The fuse in a standard set up powers the ignition and the fuel pump; the connections can corrode over time so worth cleaning them and checking the fuse.

 

Is your ignition switch OK ?

 

The other thing it could be is water/ blockage in the tank although a filter could trap this.

 

You don't say if you run lucas or bosch. I have only run a Bosch set up and presumably the Lucas pump has specific issues whcih others will tell you about.

 

Good to know i am not the only one out there !

 

Snowy

[RobinTR6]

Judging by your previous post you didnt get to the bottom of the problem, ie accurate diagnosis, so whatever it was last time is still there (I assume). Snowy gets you off to a good start, it does sound like 'electricks' or 'blockage'. When its losing power can you hear the pump, whether its Bosch or Lucas normally its quite audible when running. Is it fighting ie blockage or running more slowly 'electrical'. Obviously if you have a fuel pressure gauge you can see the pressure drop when driving. If you can eliminate the electricks, when I had a similar problem I wired the pump direct from the battery including the earth thus eliminating any connection/fuseing issues. Interestingly mine turned out to be a combination of a weak earth to pump and a sticky PRV. Mind you took me a few weeks to get to the bottom of it.

 

Let us know how you get on

[Peter Cobbold]

Darren

""......coming off a roundabout with the clutch dipped to change gear the engine cut out.......................put my foot down hard again in second. After a few seconds the power came back (with a blast and a bit of a backfire),............when it happened it felt similar to what happens if the choke is left out too long.""

Your descriptions suggest its drowning on a way over-rich mixture for brief periods after lifting off the throttle. The fuel cam follower in the MU might not be lifting when you lift off the throttle, giving far too rich mixture.- i.e. it sticks, stopping the diaphragm from pulling it up. Its behind the rectangular plastic cover - spray some WD40 in there.

But it might also be electrics....

Peter

[snowric]

Darren final thought. Peter told me this earlier this year when the rear seal in my metering unit gave up suddenly and spectaculalry. If the return pipe from the MU to the tank gets blocked it forces the engine to run rich so give this a blow though too.

 

Peter - can this happen intermittently eg if there is something in the MU blocking the return.

 

However if you really are running that rich I assume you will see lots of black smoke from the excess fuel.

[Guest ntc]

Darren

Always start with electrics first,Ht side ie rotor arm cap, leads,etc then Lt side,most mess with the Pi system and go backward from there

[TR5tar]

Thanks for your thoughts Snowy, Robin and Peter.

 

I have been wondering about loose connector, earth or failing fuse. I suppose one of those would be a good explanation of the original "going over bumps" problem, but what I experienced yesterday was much more than that. Nevertheless, that doesn't rule out such a fault.

 

I know it's possible to buy fuel pressure testers, but I haven't a clue how to use them, so might have to get some guidance on that, although before going further with that I'd like to test the electrics.

 

I am a novice when it comes to electrical and mechanical things, so I'm also going to have problems locating the fuel pump connectors and earth. Maybe the first thing to change is the fuel pump fuse (you'll be relieved to know that I can manage that without direction - at least I think so).

 

As for what type of fuel pump I have, I'm not exactly sure. I think one of the previous owners said it was a Bosch (I'm not sure if Colin changed it to that Robin).

 

You are right that I didn't get to the bottom of the original problem Robin. I know I should have, but when it was then running fine, I hoped it had sorted itself. I cannot say for sure whether the fuel pump was still running when the car cut out / lost power. I'll try to listen next time.

 

I have run the car in the garage this morning. Fuel pump kicked in as usual, it started fine, idled with choke out as usual, idled with choke in as usual, and after about 10 minutes the temp gauge was at half way. Fan kicked in as usual. I revved it for a while, as well as holding it at 2000 revs for a few seconds. There was no loss of power or anything odd that I could detect.

 

I've had the back panel out of the boot and took the following pictures:

 

 

 

I imagined that this was the fuel pump. But I'm not seeing any electrical connectors or wiring, so it probably isn't That being the case, where would I find the pump?

 

There are connectors the tank itself:

 

 

 

However, I thought that these were probably to do with the fuel gauge.

 

I have to say Peter, aside from the original problem - which might be unrelated to yesterday's experience, I was wondering about the MU / fuel mixture. It almost felt like when I tried to accelerate I was pushing more fuel into the engine than it could quickly burn. That's just a gut feeling, not based on any knowledge. I didn't spot any black smoke behind Snowy, but then I wasn't looking too closely as I was too engaged with trying to get it going, rather than stopping on a fast road. I remember years ago having a problem on a car (can't remember which), where sometimes I'd press the accelerator and not get any power, but then on lifting the power came in. Sadly, I can't remember what caused it or how it was fixed. This problem does feel a bit the same as that, so I think it is worth following up on.

 

Where then is the MU with the plastic covering, Peter? If I can find that, I can certainly do some WD40 engineering.

 

Thanks again.

 

Darren

[snowric]

Darren,

 

Your photo shows a fuel filter inside the boot so your fuel pump is presumably outside the boot behind the wheel. I think your set up is how Enginuity do them.

 

The black and white wires goign inot the tube are the original loom connections for the petrol pump follow them out and you should find the fuel pump.

 

The other photo is the fuel tank level sender to the fuel gauge.

 

Neil is right to mention the electrics, these things can often be ignition electrics related and not Lucas Injection - so check the connectors on the coil and the fuse which supplies both the ignition coil and the fuel pump.

 

I would not mess with the plastic cap on the metering unit or the rotors underneath (I've done that - guaranteed disaster from my side).

 

 

Good luck and sorry not to be more helpful,

 

Snowy

[Peter Cobbold]

Darren,

Its an intermiitent fault and they are the trickiest to track down. Measuring fuel pressure wont tell you anything much, especially as it runs OK most of the time.

Electrical gremlins are always possible, but the over-rich synmtoms suggest to me the pump is OK. Could be ignition cutting out. Check the connectors to the coil and distrubutor for corrosion. But my money is elsewhere:

 

That back fire is a clue - in exhaust I presume. It suggests to me there's lot of unburned fuel got into there while you were lifted of the throttle. A way way over rich mixture can do that. A dead spark can too, but a backfire is less likely if fuel flow has reduced upon the throttle closing

 

The Metering Unit is at the base of the distributor. Looks like this:

https://www.canleyclassics.com/images/diagrams/tr6late/20-55.jpg

The rectangular cover is awkward to move as the bodywork gets in the way of the screws

Instead try WD40 spray into the vent pipe numbered 148946. It should creep down the the cam/rollers.

 

Good luck.

Peter

[Peter Cobbold]

Darren

Is that aftermarket inertia switch still in the circuit to the pump?

http://www.tr-register.co.uk/forums/index.php?/topic/48807-power-loss-over-bumpos/?hl=bumpos

 

If so I would suspect that first of all. I know you now get a dead engine without going over a bump, but that switch could cause that too if its contacts are iffy. Bypass it by connecting the two wires together making certain they are well insulated.

 

Peter

[marki]

Hi Darren.

After a few hiccups I'd agree with Neil and start with electrics before delving in to deep.

Good luck Mark

[flatlandsman]

With the greatest respect to all those above and to answer popular misconception number 436, there is NO fuse in line with the power supply to the fuel pump on the PI system.!

 

Very unlikely to be metering unit & being a TR5 you wouldn't normally have an inertia switch fitted??

 

How old is the fuel in your tank? Are you aware of the E garbage that is diluting modern fuels and the problems this is giving? If your tank hasn't been out for a few years, I would respectfully suggest that you diagnosed the fault yourself in your first post.

 

I suggest you have an intermittant blockage exaserbated by running over a bump or cornering hard which ensures that the particle is simply blocking the fuel feed to the outlet. This tends to happen when under power as well as obviously fuel delivery requirement increases. When stationary, it's very likely that the offending 'lump' will not impede as fuel demand is much less.

 

Suggest you get a borescope or similar and have a look. Alternatively get a large flat tray in the boot and remove the tank union, watching carefully to see what comes out. If there's evidence of sludge or particles, then it's tank out time I fear!

 

Not actually a difficult job and it's at the best time of the year when you very likely won't want to be driving your car on salted roads.

[RobinTR6]

All good inputs. You need to structure your diagnosis. Try as suggested removing the tank exit pipe and ensure you have a steady flow. Shine a torch down through the cap and you should be able to see any debris, if there is any. The white wire is the positive to ignition switch which is now going through the newly added cutout switch. I'd remove the wires to it and bridge them thus eliminating the switch. Check the terminals exiting the pump and those in the picture. The pump is on the outside of the chassis leg behind the nearside wheel. As I opined earlier , try wiring two new feeds direct from the battery, pos and earth straight to the pump terminals eliminating any issues with the current wiring, be mindful that you will have pump permanently on when trying this. Report back. I'd leave the MU diagnostics till later, from memory its a newish MU so shouldn't have any problems.

If the feed from tank is clear and the electrics can be eliminated and its still an issue we can move on to the pump filter, pump and pipework, after that its back to the MU, Prv, and associated bits.

[LGFromage]

Judging by the installation in your car I would have thought that the fuel filter should be on the pressure side of the pump rather than the suction to avoid any compromise to the flow entering the pump. A partially blocked filter upstream of the pump has a worse effect than one downstream because, for the latter, the pump is working more efficiently.

 

Whilst this suggestion may be useful it is just one of the points for consideration in resolving your car's problem. Good luck with your efforts and please let us know how you get on.

 

Tim

[TR5tar]

Thanks for all the additional comments.

 

As it's an intermittent problem and it's not clear what the cause is, I have to be a bit pragmatic about it given that I'm not that knowledgeable. Therefore, as there have been several suggestions regarding the electrics and as I feel a bit more confident with them, that's where I've started. I've replaced the fuses for the fuel pump and coil, and cleaned the terminals on the pump relay with contact spray. I've also cleaned the terminals on the coil. I've checked the wiring and connectors from the electronic ignition box to the distributor and then to the coil, and all that looks OK to me. There are a couple of wires that are not attached to anything, but I think they were like that when I bought the car, so I do not imagine they are an issue. I've had the distributor cap off and nothing looks amiss to me in there.

 

I've shone a torch down into the fuel tank and I can't see any debris. It all looks pretty clean. I have one of these cheap borescopes that I could put down there, but I'm a bit worried about doing that. Isn't there a danger of fire? I've not removed the fuel tank exit pipe yet. If I do that (and there's no blockage) will I get a lot of fuel pouring out?

 

Before doing more with the fuel tank, I want to check the pump terminals. When you say that the pump is behind the nearside wheel Robin, is that the back wheel?

 

I've not taken the car out again, but have run it in the garage a couple times more without any problems. I can hear the pump and it sounds as it always does.

 

Will keep you updated.

 

Thanks, Darren

Edited December 17, 2014 by TR5tar

[RobinTR6]

Yep nearside rear wheel.

[Peter Cobbold]

I would be very wary of lowering a borescope into a petrol tank. Although undisturbed vapour should displace air and so not be ignitable until the fuel is long way below freezing point, I'd not take the chance... one stray spark might hit lucky in a patch of air-petrol mixture. The modern scopes have power for the camera and light running all the way to the lens.

Peter

Edited December 17, 2014 by Peter Cobbold

[TRE]

a good few years ago I suffered similar symptoms in my V6 Tuscan. It was eventually tracked down to a break in the LT lead twixt coil & distributor . Replacement cured the problem permanently. Worth a try!!

 

regards

 

Richard

[boxofbits]

I would go for electrical diagnosis first, and I think Peter is starting at the thick and expensive end of the wedge first.

 

It is not necessarily a mixture problem. My TR4A suffered very similar problems, and the cause was the coil. Both the coil and condenser can cause backfiring, if you still use standard ignition, and unless you are seeing exceptional blacks clouds of smoke in your rear view, it may not be worth disturbing your MU until you have ruled out other possibilities.

 

Check your plugs first to see if they are sooted or evidence of excess fuel. They should be a mid brown.

[Peter Cobbold]

I would go for electrical diagnosis first, and I think Peter is starting at the thick and expensive end of the wedge first.

 

 

I'm inclined to agree now - after learning its on electronic ignition...

Peter

[TR5tar]

Quick update. With Christmas looming I'd not got chance to do much more on locating the fault, but as the weather is nice at the moment I thought I'd roll the car out and do a bit more (before I'm too full with Christmas dinner).

Last week I changed the plugs, not because I thought that was the problem but I wanted to upgrade to the iridium fine wire ones that have been talked about in another thread. My old plugs (BP6ES) look OK; four are brown/grey in colour, with the other two being a bit blacker. I went for the NGK BPR6EIX replacements, which I haggled down at Euro Car Parts from £55 to £46 for six. Didn't think that was too bad a price. I cleaned up all the connections on the HT leads at the same time, and also changed the Rotor Arm.

Today I've had the back, nearside wheel off to look at the fuel pump. I couldn't see any issues with the pump (it still sounds like it's running fine) . . .



Here's a picture, just so someone can confirm that I am looking at the correct thing.

If there are terminals on the pump itself, then I couldn't see them or get to them, but I followed the wiring back into the boot (the black and white wires mentioned by Robin) and cleaned the connectors on them. I did notice that the black wire that attaches to the fuel tank (which I assume is the earth for the fuel pump) was a bit exposed at the tank, so I put some insulating tape around it and a plastic tie to keep it tight in place. I do carry a lot of stuff in the boot, so it made me wonder if perhaps some of that was banging against that earth wire and disturbing the connection. Would I be right to say that if the earth wasn't working properly that would be enough to stop the pump?

 

I'm not sure what to do next. I suppose I should run the car out to see how it is working. Everything seems fine running in the garage, but it's on the road that the issues manifest themselves. I am a bit nervous about heading out at the moment.

 

Given the situation, I have a separate question on towing. Firstly, are there any good tow points on the TR5? Are there any problems associated with towing TRs? I ask the second question because I'm sure I read something about disconnecting the driveshaft before towing.

 

Thanks for every ones input.

 

Cheers, Darren

Edited December 25, 2014 by TR5tar

[RobinTR6]

Darren, merry Xmas. Yep that's the pump , black and the fuel filter. The earth is critical on the pump so yes that could easily cause the problem. If you're satisfied the ignition is OK, rotor arm etc I'd still wire direct connection from the battery earth and positive direct to pump terminal which will eliminate or identify any problem there. The pump takes 10amps + and must have good feeds. Even a bit too much resistance in the earth can reduce pump pressure albeit that would be most noticeable up the rev range and be consistent. Anyway replace the earth and see if that does anything.

[Guest ntc]

Quote, boot (the black and white wires mentioned by Robin) and cleaned the connectors on them. I did notice that the black wire that attaches to the fuel tank

 

The black wire should not attach to the fuel tank.

[TR NIALL]

Neil's right,take that Earth Wire off the Tank and find a better location for it.

[TR5tar]

Merry Christmas Robin. I hope you had a good one.

 

I'm not absolutely sure that the ignition is OK, but I aim to get behind the dash to check those connections next if I can. After that I will need to get some wire to make the connection direct to the pump that you suggest. Before I do that, I think I will run the car out to see if I am still having issues. One thing that did strike me recently is that the going over bumps problem occurred when the back wheels hit the bump, so I think that would suggest problems with the connections at the back.

 

Merry Christmas to you Neil and Niall, too. Thanks for your inputs. I misrepresented things a bit when saying that the earth is attached to the fuel tank. It's actually attached where the tank is bolted to the body. It can be seen in picture #3 in post #7. Does that make any difference to your suggestion that it should be moved?

 

Thanks Darren

Edited December 26, 2014 by TR5tar