Hi, I've not been on here for a while but now doing another kit with my lad and have an engine problem and wondered if anyone was good at diagnosing?

1.6 efi, starts and idles ok, revs fine whilst stationary.
Drives ok for a short distance then it reduces power and throttle response. Dipping clutch and revving does not go past 2000 revs.

turn engine off, leave for 10 seconds, restart and then it drives as normal again.

I've changed spark plugs, leads, fuel filter and the tank has been checked for its connections and all look ok.

I'm thinking it might be the CAT breaking down or the fuel pump but it drives ok for around 5-8 miles before the above happens.

Anyone got any ideas?

Check the pickup in the fuel tank is not sludged up.
Check the fuel cap vent or tank vent is working correctly, as a vacuum building up will cause similar problems.

Dave

It is not the cat, if it was engine would be reluctant to rev as soon as you start it.
You need to do some proper diagnostics rather than shotgun blast random parts at it. Basically you need to know if it is fuel or ignition, from the symptoms it souunds like fuel so check that first.

If you don't have a diagnostic port but the system has a Schrader valve on the fuel valve I would check the fuel pressure while it is acting up. If you don't have a Scharder valve then you would need to use a T adaptor to connect a gauge. BERGEN FUEL PUMP PRESSURE TESTER for Schrader Test Port Systems Petrol & Diesel
If you don't want to do this but have a decent DVOM check the Lambda upstream sensor voltage output. Normally on a warm engine the Lambda sensor output should dance up and down between about 0.1 and 0.8 seconds. If the engine is running lean it will read below about 0.45 volts, if you see the voltage flatline about 0.1 or 0.2v you have a weak mixture.

It could be the tank air vent or free floating debris in the tank covering the tank suction. If it is disconect the fuel lines and blow them back in the reverse direction of flow followed by cleaning out the tank and fitting a sock filter over the suction tube in the tank should fix it.

The other test you can do when it is acting up is check the spark voltage --- if you pull a plug lead off the spark should be able to jump about the width of your thumb to earth.




[Edited on 18/11/16 by britishtrident]

[Edited on 18/11/16 by britishtrident]

Easiest starting point there would be to leave the fuel filler off and go for a drive.
Feel the coil for heat.

Then follow^^. Won't be the CAT.

I'm not an engine person, so don't know why I'm even getting involved but...... are you sure this isn't a fault code being generated and the engine ECU going into limp mode????

Are you tuning the original ECU?

Jason.

As above,sounds like limp mode.

Have you got the original dash/clocks to show up a engine management light?

Thanks,

It's on my Daihatsu SPortrak 1994 and no warning lights visible.

Coil isn't hot.
I'm not doing anything to the ECU.

It could be the breather but as nothing has changed, I'm thinking that unlikely having checked that the pipes aren't blocked.

Regarding the tests mentioned, I have no idea how to perform those, nor the tools required.

Spark appears to be good on all 4

Tank is aluminium and the pickup is on the side of the bottom part of the tank. No blockages or debris here.

Sounds like limp mode to me, with an intermittent fault, probably a faulty sensor or connection, ie cam signal or tps signal. You could try reading the fault code from the ecu just google and there's some instructions to short out the obd port to get the engine management light to flash a code. I would probably also check the connections to the engine sensors, if you can get a couple of replacements cheap then swap them out and give it a go.

The truck will be OBD1 at best that means minimal diagnostics
You will only get stored flash codes from OBD1 if the MIL is illuminated.
Even if could you retrieve flash codes from it they won't tell you much.
It is not in a limp home mode if it were the MIL would not only be illuminated but flashing.

The age of vehicle makes a fuel delivery problem most likely cause.
A heat related failure such as the coil is possible but more unlikely because this would usually result in the engine either dying completely or misfiring severely not restricted power and RPM.

Not all limp modes light up the EML,my skoda doesn't

quote:

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Originally posted by CosKev3
Not all limp modes light up the EML,my skoda doesn't

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Yet again British Trident you can across as a right tool,, the OP asked for ideas on what might be the issue, communicated in a manner he'd understand, instead you post a definitive response that in your eyes is right even if it's wrong, then justify it by counter arguing with others who come from a different angle. I trust that the OP will look at the posts in a measured manner and make his own decisions based on the ideas posted in the thread. I have stopped posting like so many others because of your terrible attitude to others and berating nature of your posts. I posted on this occasion so the OP got a balanced view rather than your "I'm always right" posts sending him down a dead end."

I every forum seems to have someone like you who is tolerated rather than respected and who add nothing to the mix. If it was my forum you would have Been gone a long time ago.

To the OP, all the best with sorting the issue out.

quote:

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Originally posted by B33fy
Yet again British Trident you can across as a right tool,

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Many thanks to everyone.

I don't have access to the tools necessary without putting it into a garage that will likely charge me north of £45 an hour to fiddle with this and that and may still have the issue.

Things I can try before going down this route I think are:

1. Disconnect the CAT at the manifold end and make a gap so as to test restrictions when hot
2. Check the fuel pressure either with a gauge or more crudely a stopwatch and measuring cup (once it's at temperature so not to get different fuel / air mixture as it warms)
3. Re check the spark plugs and leads
4. Disconnect the fuel pipe just before the pump and see if there is any crap in the filter (if there is one) and check pickup in the tank
5. Distributor change?

After this lot, I question whether it then becomes viable. It's only worth a few hundred quid (or more importantly the ability for my 10yr old to learn to drive in the field)

quote:

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Originally posted by obfripper
Check the pickup in the fuel tank is not sludged up.
Check the fuel cap vent or tank vent is working correctly, as a vacuum building up will cause similar problems.

Dave

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So long as there is a means for the pressure in the tank to normalise there should not be a problem, where i have encountered problems like this involving vacuum build up, just removing the cap and driving around will temporarily cure the fault.
The next option if possible would be connect a fuel pressure gauge and drive around until the fault occurs, if the pressure drops off as the fault occurs then you have isolated the fault to the fuel feed system. The running pressure will vary according to throttle operation in the range of 2.3-2.8 bar from idle to full throttle.
If the pressure drops, with the engine still idleing listen to the fuel pump to check that it is still running and whether it sounds strained. The engine can maintain idle with the pump not running for 20-30 seconds before stopping.

The carbon canister is there for fuel vapours to be drawn into the engine instead of being vented to air, this doesn't allow air back into the tank. You can remove this and blank off the pipe on the inlet manifold it is joined to, but it is unlikely to adversely affect the running of the car even if faulty.

In my experience a coil fault can cause similar faults, but they would not go back to normal in 10 seconds, you would be looking at a 10min+ wait before you could restart normally.
Your engine has separated fuel and ignition controls, the fuel injection uses a pulse from the distributor for the engine rpm signal, so a low tension ignition system fault should stop the engine completely.

I have also found this which should help you get any fault codes with nothing more than a paperclip.
Because it is not obd compliant and an old efi system, the fault codes are quite limited in what they will tell you but will be a starting point if nothing else.

Dave

You say it's an aluminium tank ? Is it inside the car and definitely no chance of it uncovering the pickup as you drive it ? Re starting after a few seconds does sound more fuel related than ignition as the only thing left to try would be the ignition amplifier but they are usually pretty reliable on these

Thanks,
I'll give that a go tomorrow night.
I think I've been a bit of a wally and forgot about the tiny filter before the pump.
My lad mentioned something about filters after school on something totally unrelated and it got me thinking.
So I went out and disconnected the inlet pipe to the pump and there was a tiny filter and guess what - it's full of crap.

Now cleaned out but ran out of light to take it for a test run (untaxed so got to use the field but don't want to upset the neighbours with lights going round and round) so will let it run to temp tomorrow and then whizz it round and round and see what happens.

As a precaution, I have ordered a new distributor cap and rotor arm as I'd planned to change these anyway.

I'll update results once tested and checked the engine codes as per above.

My fuel tank has an additional small bowl underneath to act as a pickup whilst at angles etc and its outlet pipe is about 1cm off the bottom edge on the side so I'm really surprised at the amount of crap in the tiny filter.


Does the fuel pump really only pump out to around 3bar? Seems really low for an EFI system.

3 bar is pretty common for most efi systems

To summerise
(1) The engine starts and runs normally until the fault appears.
(2) We know it is time or heat related.
(3) After a very short rest time the engine will re-start and run normally
(4) The problem is decribed as loss of power/restricted rpm not a misfire or cutting out.
(5) The truck is older higher mileage, with very limited diagnostics.

Faults that cause loss of power or restricted RPM that we can eliminate immediately
Cat/restricted exhaust as this would cause loss of power from initial start up.
Vacuum leak as this would be present from start up and usually reduce to some extent as engine warms.
Apparently no regular misfire reported and plugs and leads have been replaced which eliminates plugs. leads and injectors.

Also as the engine runs but with restricted power the following are unlikely.
Crank Position Sensor/ignition trigger --- normally inductive crank sensor faults show up as long crank times or non-starting.

So by elimination we are looking at either a fuel delivery issue or a heat related failure.

Taking heat related failures first.
Loss of spark or injection due to over heating electrical or electronic part, isn't impossible. The parts that could fail when hot include the coil, ignition amplifier and a hall effect crank sensor or a fractured soldered joint in the main relay which is common on some Aisian cars especially Hondas. However this class of problem tend to cause complete engine shutdown when warm or in the case of the main relay failure non-starting when warm rather than restricted power. Also fault clearing after a very short recovery time is circumstancial evidence against this.

So the balance of probabilities lies with a fueling issue.
An electrical failure of the fuel pump or the pumps non-return valve would normally show up as a long crank time or non-starting.
The coolant temperature sensor although it has an important role in fuel but is more likely to lead to over fueling and the very short recovery cooling-off time makes this being the cause highly unlikely.

The general description of the fault is a good fit for a restriction problem on the suction side of the fuel system but the possibility of an electronic problem can't be elininated.









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[Edited on 23/11/16 by britishtrident]

Finally got around to testing it after being away on a course.

Really embarrassed to say that it was the tiny in-pipe filter that was blocked.
Got it taxed yesterday and let it run up to temperature tonight and then went for a longish drive, certainly long enough for the proble to manifest itself previously. Hey presto, it now runs fine.

So i've ordered a better inline filter to replace this one in the pipe.

Huge thanks for all your replies