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pedjoni

1.6 Gti - Hesitation And Strugling While Aceleration

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pedjoni

Hello everyone,

 

Recently my pug develop a problem. I will start from very beging. It is cabrio model 1.6, 76 kw , 1986 year.

Problem accured after changed fuel pressure regulator ( mine was leaking , I had problem starting from how , after sitting for a while ).

After that, car couldn t acelerate, hesitete at all rpm, then sometimes when I push gas pedal to the bottom it hesitates but it will go a little.

I replaced FPR with another one, same situation, then put back old one (car was running great but hot start problem) also the same situation.

Because in my city , no good mechanic for pugs I was checking all sorts of thing alone. Only one mechanic helped me little bit( I ll explain it later).

After all of that a replaced few parts, which I consider could be problem:

 

- Spark plugs new

- Coolant temp sensor new

 

I ve also buy two second hand AFM , in good working condition, problem persist.

This mechanic tried and turned spring on afm , car is now running good until 4000-5000 rpm but after hesitates no power at all.

And this made my mpg horrible. Can anyone had similar experience or advice that could help me.

 

Thanks in advance!!!

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PhilNW

Check the fuel pressure it may be the pump not the regulator that's at fault

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dcc

Check the rotor arm and points for wear, oil ingress and corrosion.

 

Had a similar problem on a friends motor about 12 months ago!

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pedjoni

Thanks for replies, rotor arm and distributor cap are new also, I ve replaced them.. There is no signs of oil in distributor... I have spare fuel pump, back in my home town, as soon as I get there I will try it... How much fuel pressure supposed to be ? how much bar is dlivering by the fuel pump? i know that FPR is 3.0 bars...

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dcc

You'd need an inline gauge of some sorts to measure the pressure.

 

Personally id remove the fuel hose and place into a container, get a friend to crank and see how much fuel comes out. Should be a nice steady amount. If all ok, next i would remove all injectors, put them in glass jars and retry cranking the engine, make sure equal amounts of fuel in each, get a friend to crank and check to make sure each injector has a good spray pattern.

 

If all ok here, id be inclined to go back and look at the fuel pressure reg. Is it possible youve fitted a 3.5bar item? Id also check your dizzy rotation to be sure its running correct, as well as the vacuum advance unit

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PhilNW

Thanks for replies, rotor arm and distributor cap are new also, I ve replaced them.. There is no signs of oil in distributor... I have spare fuel pump, back in my home town, as soon as I get there I will try it... How much fuel pressure supposed to be ? how much bar is dlivering by the fuel pump? i know that FPR is 3.0 bars...

 

Max pump pressure is around 3 - 3.5 bar.

 

Only way to really test is a proper pressure gauge., you can gently clamp the return flexi pipe from the fuel rail to see if it affects the delivered pressure.

 

How old are the pumps? The spare may not be much better than the original but worth a try (after a problem with my old pump I got a spare of ebay but it was worse than my original, brand new bosch solved it)

Edited by PhilNW

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pedjoni

Hi everyone . I ve checked a lot of things. But I noticed on bottom of FPR where is conected fuel return line , when I disconect it , there is no fuel returning back to tank. Even when I press hard on gas, whem it is supposed to exess fuel and deliver it to tank. I think my Fpr is bad, and I am assuming that there should be fuel returning to the tank ? Correct me if I am wromg , thank you

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jackherer

If your pump is weak there wont be any excess pressure to be relieved by the FPR so you wont see any fuel in the return line.

 

If your FPR was somehow blocked and not returning fuel to the tank your fuel pressure would be very high and your car would overfuel, i.e. there would be grey smoke from the exhaust! Your symptoms sound more like a weak fuel mixture.

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pedjoni

I have smoke from exhaust , and area upfront on fender from exhaust is black. So i am assuming my fpr is blocked...

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jackherer

Did the smoke and black soot markings start before or after the mechanic played with the spring in the AFM?

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pedjoni

Now on my car is other afm, which is set by factory , it is not moved spring or anything... It is doing rhe same...

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PhilNW

Get a pressure gauge to check what is really happening sounds like low pressure to me so fpr will have little effect

Edited by PhilNW

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pedjoni

Hi everyone,

Litle update.

I tried changing fuel pump and to make long story short. Just putet back old fuel pump, and my spare AFM, car is now running good. Somehow its is fixed but I don t know how. I ve changed those things also earlier, but with no change.

But now I have other problem, car is running too rich I think. It goes well, all the way to the redline, no strugling or hesitation. But my fuel economy is very bad...

I ve checked spark plugs today, i saw carbon build up very much. Runing rich I pressume?

What to check ? CTS is new?

post-26247-0-58032400-1510504905_thumb.jpg

post-26247-0-57881000-1510504914_thumb.jpg

Edited by pedjoni

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PhilNW

Did you checked the fuel pressures?

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pedjoni

Today I bought parts for check fuel pressure. Not so good.

1.5 bar so fuel pump is bad ??? But car goes very well, very strong aceleration. I am confused.

here is some pictures:

post-26247-0-94569600-1510767260_thumb.jpg

post-26247-0-65086200-1510767276_thumb.jpg

post-26247-0-45551000-1510767289_thumb.jpg

post-26247-0-27791100-1510767297_thumb.jpg

post-26247-0-48390200-1510767406_thumb.jpg

Edited by pedjoni

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PhilNW

At that pressure mine was running very rough whereas the plugs suggest the opposite 

Does the pressure vary with engine revs? There should be a small variation 

Try slowly clamping the return pipe to see if the pressure varies.also do the same on the feed pipe

Possible it's a dodgy gauge of course

Edited by PhilNW

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wicked

Note that the fuel pressure is regulated against the pressure in your inlet; if it is -0,6 bar at idle and you measure 1,5 bar, the actual fuel pressure is 2,1 bar. (which is on the low side). Keep that in mind before you draw conclusions.. 

Second note; never trust the lower range of a gauge. If you want to measure 3 bar accurate, your gauge should have a max range in the 5 bar ballpark.

Edited by wicked

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welshpug

yes 1.5 is too low, should be 3 bar.

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wicked
4 minutes ago, welshpug said:

yes 1.5 is too low, should be 3 bar.

3 bar + MAP (~-0.6) = 2.4 ish bar at idle.

Replace fuel filter; put back the original pressure regulator and measure again. If still low; replace the pump. 
Note that DFZ pressure regulators are 2.5 bar iso 3 bar; don't grap the wrong one. 

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welshpug

you should disconnect the vac line when testing btw.

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Rob_the_Sparky

Any reason to have the car even running when testing?  That way you do not need to disconnect the vacuum.  (might need to supply 12V to the pump though to ensure it is running)

Bigger question would be why is it running rich with a 1.5bar pressure, it should be running horribly lean.  Either:

that reading is wrong,

there are other problems masking the reading

or someone has been hacking the car to make it run not knowing what the root cause of the problem was.

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jackherer
40 minutes ago, Rob_the_Sparky said:

or someone has been hacking the car to make it run not knowing what the root cause of the problem was.

 That's been the underlying problem in this thread since the first post mentioned the spring in the AFM.

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pedjoni

Well, I bought new pressure gauge, maybe it is wrong. On the car now is AFM which nobody touched. It is on factory settings. Car runs fine, aceleration good all to the red line. Only problem is at idlee. IT idle too low. Screww on the throtle body is almost all way out to keep it going without stalling. Fuel consumtion is terrible. it is well over 15 l for 100 km... When I press gas pedal hard, there is black smoke like diesel engine, past 5000 rpm. also notice unburned fuel bang from exhaust.

Today I bought starter spray, to fing maybe vacuum leaks. I was spraying aroung inlet manifilod, injectors, throtle body.... No0 rpms changed, so I gues no vacuum leak also...

If fuel pump is bad, under pressure, I assume, car wouldn t acelerate good????

 

Also when I disconected return line from FPR there is no fuel, line is completely dry o.O
Fuel filter is new.
 

Thanks all for replays

Edited by pedjoni

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welshpug

when are you checking the return line?  with engine running?

 

where did you install the pressure gauge?

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pedjoni

When engine is running. I conected gauge between fuel filter and fuel rail???

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