We have an old diesel Hyundai Santa Fe and the problem, which I didn’t notice for a while but which has become more obvious recently, is this. When you start the car from cold, it turns over fine – the battery is strong – buy the accelerator is unresponsive. You can’t “pump it” before you turn the key to help get fuel into the engine to aid starting. This means that the engine starts using only whatever fuel was already right there in the pipes and what gets pumped in by the fuel pump under “idling conditions” – if that makes sense?

The car will start on the second or third attempt and then run at tick-over speed (accelerator still not doing anything) for anywhere between a couple of seconds to, more recently, a minute or more. Then the revs pick up a bit and the accelerator kicks in.

Google suggests things like the throttle position sensor if your car goes, or has gone into Limp Mode, but I can’t see anything explaining the temporary failure of the pedal to respond.

Added feature – if you start the car, the accelerator doesn’t work and you stop the car and start it a second time, it generally works straight away.

Any advice is appreciated, otherwise it’ll be the garage on Monday and I’ll be at their mercy 🙁

You have not been able to pump the pedal to add “more” diesel since mechanical fuel pumps stopped being a thing

The rest sound like the TPS or the being Hyundai -probably the ECU it runs through.

Pumping the accelerator pedal? Its not the 80s grandad. Things move on and on most cars ignition fuelling is governed by the ecu till the emgine fires, plus say half a second.
What ypu describe is tps sensor failure if its fly by wire. Or, as its churning amd not catching a nrv failure, fuel cut off solenoid failed.
Allows fuel to return to the tank, then needs a few seconds for the hvlp pump to get it going round the system and to the hp pump

You can’t “pump it” before you turn the key to help get fuel into the engine to aid starting

To me, that’s normal (not pumping it) for every diesel I remember. I think the last one I had, the manual specifically said don’t touch the accelerator until it’s started.

(accelerator still not doing anything) for anywhere between a couple of seconds to, more recently, a minute or more.

The couple of seconds might be normal, but the minute isn’t.

Actually, could be glow plug relay control safety quirk.
If the glow plug ecu fails then it will start but takes 2 or 3 periods of cranking. Then the engine runs badly for a min till the tips retain heat.
On normal start up the glow plugs will run for say 90 seconds then auto power off. Even if the engine starts agter 5 seconds, the glow plugs stay on to aid smoother cold driving and clean up the emissions.
Maybe yours has a failsafe mode where the pedal stays unresponsive till there’s some heat in the engine.
Switch it off then on again and its not a cold start, so normal operation resumes.
Got a multi meter?

My mum’s i10 did exactly that when the fuel return valve was failing. I know it’s petrol vs diesel but it may be a Hyundai quirk where low fuel pressure disables the throttle. I had to fit a new fuel pump as the return valve was built into it, the fuel rail would leak pressure when the pump wasn’t running and would take a few seconds to repressurise the system before it would respond to throttle inputs. Starting always took a few seconds too while the pressure built up enough to let the injectors fire.

Edit: singetrackmind has similar thoughts.

You can’t “pump it” before you turn the key to help get fuel into the engine to aid starting

Yeah petrol cars haven’t worked like that since the 80s and diesels never have 🙂

“You have not been able to pump the pedal to add “more” diesel since mechanical fuel pumps stopped being a thing”
“Pumping the accelerator pedal? Its not the 80s grandad.”

🙂

So every time I’ve done that, which is every time I’ve started my various cars over the last 30 years, I may as well have been tapping my head and muttering “touch wood” 🙂

I am old, as is my car, but I’m happy to have learned something. I assumed pumping the pedal was the equivalent of pulling out the choke – which is how you have to cold-start the old diesel pickup truck at the campsite I sometimes work at.

My big fear is hearing the phrase “it’s the little black box mate, can’t be repaired has to be replaced – that’ll be a grand please”. 🙁

I do have a multi-meter, but if it’s any sort of sensor that need replacing then I guess it sounds like a job for a mechanic who knows about these sorts of things.

My diesel To Iran did that prior to it finally dying. Would start but the accelerator would do nothing and eventually it would stall, other times it would start normally. Turned out everything was completely sorted up, guy I sold it to (as a non runner) spent about a grand on parts to get it working again, DPF amongst other things. Get it properly checked now before it strands you.

Have you plugged a code reader in yet? That should narrow it down a bit.

Glow plugs. Slowly gets worse, and you don’t ‘notice’ until you do then you realise it doesn’t want to start readily. We’ve also seen night time/morning temps dip this last week or two so it’s more evident

Even my 20 year old Nissan is all fly by wire. I suspect one of a number of possible failures – code reader is your friend, provided a code get’s thrown. My car suddenly decided it wasn’t going to start on first turn of the key. Started but had no power. Managed to get the car home, but only when near home did a light come on. Code reader – crank shaft position sensor. Bought a genuine set off ebay, crank and cam, realised on changing that my car had never had them changed (subject to a recall). All OK.

A lot of electronic repairs aren’t that bad. The code reader says that the sensor is bad, replace cheap sensor, jobe done. Not all of them, mind…

I assumed pumping the pedal was the equivalent of pulling out the choke – which is how you have to cold-start the old diesel pickup truck at the campsite I sometimes work at

Not wishing to rub your nose in your mistake (and not helping the original question at all!) but I find these things interesting. I vaguely remember being told that depressing the accelerator on some car or other activated the automatic choke, but I’m not sure if that was correct. On fuel injected petrol cars though, there are sensors in the intake and exhaust so it knows exactly how much fuel to inject given the conditions, so a choke is not required.

Also, on old diesels the lever is not a choke, technically, it’s a cold start lever which advances the ignition timing and raises idle rpm slightly. Rather than providing more fuel for the air, as in a petrol, it just injects diesel earlier in the cycle to give it more time to burn in the cold air.

diesel To Iran

Is that a bi like coals to Newcastle?

I did wonder if Iran was specifically relevant . . .

Looks like it will be the garage on Monday then for a diagnostic interrogation.

Molgrips – did I say choke? I meant Cold Start Lever . . . . 😉

Also, on old diesels the lever is not a choke, technically, it’s a cold start lever which advances the ignition timing and raises idle rpm slightly. Rather than providing more fuel for the air, as

On an old mechanical pump hitting the pedal usually knocks the cold start out of operation

How ever on tired old engines with low compression the cold start can be a hindrance than a help.

I can close this thread now . . . .

To cut a long story short, our old car had 4x diesel injectors that needed replacing. Now they’ve been done the car starts first time, the accelerator works from the off, no smoke from the car on cold and the car runs beautifully smoothly.

They also changed the diesel filter while they were at it.

A local mechanic, not the one we’d been going to recently, plugged his laptop in and analysed the fault in no time and he recommended a fuel injection specialist to carry out the work.

Glow plugs. Slowly gets worse, and you don’t ‘notice’ until you do then you realise it doesn’t want to start readily. We’ve also seen night time/morning temps dip this last week or two so it’s more evident

i thought i had an issue with glowplugs in my touran because of staring so i waggled the wired off to find that ony one of the glowplugs had any for of connection left with the cable and clearly hadn’t operational in any way for significantly longe than the issues. i got the tool to drill them out but it being a touran it shat itself in a multitude of ways before i got round to it.