4500 GRX sudden power loss

[Florian320]

Hello!
My '99 4500 injection GRX is making some trouble. A few days ago after driving a dustroad suddenly I barely had any power.
Idle was down to about 500 RPM, the engine took gas only very slowly or not at all and sounded like it would cough.
When I pressed the pedal a bit more the engine actually became slower for a short time until it eventually accelerated again.
It felt like it would not get enough fuel.
I stopped the engine, didn't find anything and could restart it.
Now the funny thing: when I drove back on the dust road after a bigger bump the engine was digitally back to normal.
I went to the mechanic and we precautionary changed the fuel filter which was looking quite clogged with sand.

Yesterday unfortunately I happened again but in the morning at engine start. Idle around 400-500 RPM, didn't want to take gas, like coughing and again sounding like not getting enough fuel. I started driving to get to the mechanic and drove a bit harder on the dust road to maybe get it back to normal and to actually get there at all and suddenly again the engine was back to normal.
Unfortunately it didn't show this when at the mechanic's place, even one day later and driving quite some gravel road.

Does anybody have a clue, what it could be? We think of the fuel pump in the tank but before we open this it would be nice to be somehow sure.

Or did anybody maybe have a similar problem?

[Herrie]

Years ago when I bought mine I had a similar problem and the first time I stopped but did not want to switch it off because I thought that I will not be able to start it again.

I did switched it off after some time and left it for 2 minutes and it started and I could drive with no problem.

The second time - the last time! - it happened again, I just switched it of and waited for 2 minute and started it again and uptill now it never happened again.

Just over 2 years ago the engine was just misssing on the way comming back from our Botswana Outreach trip and we found that the problem was the fuel pump connector.

[ricster]

This sounds like a filter problem. You have changed the fuel filter, but how does the air filter look? The computer may be asking for air and there isn't enough delivery. The bump "may" have shaken off a bit of dust to allow airflow.

There may be a filter near the tank ( not sure as I'm a diesel chugga...hahaha) or possibly a blocked filter on the fuel pickup. I remember on my SANI there was a fine mesh around the pickup that I cleaned on time when I dropped the fuel tank.

Herrie's connector could also be a problem... good idea to check that aswell, Although I would think that it would either work 100% or not at all if not making connection.

[bogeyman]

Make sure that the engine management wiring plugs are all making good contact. A rusty plug on the heat sensor on my 4,5i made it very sick with similar symptoms. Bad signals to the ECU will give bad performance.
Graham in Centurion has diagnostic equipment and technical manuals that will find the fault quickly.

[Peter Connan]

Pretty sure it's a bad electrical contact somewhere. It could be the ECU plugs, any of the plugs on the fuel injection, possibly the fuel pump's contacts or even a bad earth.

Firstly check all these plugs and spray some contact cleaner on them, then if it does it again fiddle with wires to see if it goes away?

[Tinus lotz]

I agree with Christo and Peter bad connection on ecu or maf or one of the plugs .......
get to some one that has the correct diagnostic tools then he can download the last faults and show you in the correct direction because you have a 99 model there is a good change that the little motor running your fuel pump inside the tanks brushes are tired I think you need 3,5 bar all the time but a download will show very quickly if the feul pump is worn out .....maybe even a blocked strainer on the one inside the tank?????seeing that you saw sand ect in the filter ????I talk under correction but it is about R450 for a new fuel pump at Graham . it makes the world of difference

[Jorrie]

Florian
I see you are in Hoedspruit.
Give Graham Cumming a call and discuss the problem with him.
To me it sounds like fuel starvation, maybe a bad fuel pump or dirty filter. But, then it could also be a bad connection relating the the ECU.

[Florian320]

Hi Guys,

thanks a lot for all the answers!

What I (or the mechanic) did until yesterday:
- opening and cleaning the MAF-sensor - looked like factory new
- pulling of MAFs plug when engine is on - idle just got a bit higher, engine ran normally -> probably the MAF sensor isn't the faults origin
- looking into the air filter - that looked brandnew, there wasn't even sand in the box
- having a look on the fuel pump element through the service opening - there it was very dusty but all cables looked ok and the plug was tight.
Actually it was so tight that I didn't manage to open it to measure the cables - does anyone know how to umplug that one?

Calling Graham is on my today-to-do-list.

But: I found a loose earth cable in the engine bay, it is on the shield on the left side - could that be important?

[ricster]

That is a distinct pisabolity...haha. A poor earth can make nonsense.

[Stefan]

Hi Florian

I don't know about the Petrol models, but on the Diesel, the MAF only comes into the equation at higher speeds (60+) where it measures faster airflow and then adjusts the mix. if the MAF is faulty (mine was stuck on 1V (as opposed to varying between 0.5V and 5V)) the mixture is too rich at low speed and too lean at higher speeds.