99 A4 - hard start after new fuel pump
#1
99 A4 - hard start after new fuel pump
Hi all,
Car is a 99.5 A4 with AEB 1.8t Quattro and has 215K on the odo.
My issue is hard starting after installing a new fuel pump. Searching older posts revealed possibly a bad replacement pump and/or a bad coolant temp sensor. My question is if there is a possibly a connection I failed to make properly or if there are OBD2 values I can read via my bluetooth reader and phone app to assist in troubleshooting this (no Vag-Com access)?
Background is this:
Fuel pump died and was replaced about a month ago. Car runs great after it starts, in fact I think the old pump was very weak before it died as I had very poor performance and some drive-ability issues I was tracking that have cleared up with the new pump.
Thank you in advance for any ideas.
Car is a 99.5 A4 with AEB 1.8t Quattro and has 215K on the odo.
My issue is hard starting after installing a new fuel pump. Searching older posts revealed possibly a bad replacement pump and/or a bad coolant temp sensor. My question is if there is a possibly a connection I failed to make properly or if there are OBD2 values I can read via my bluetooth reader and phone app to assist in troubleshooting this (no Vag-Com access)?
Background is this:
Fuel pump died and was replaced about a month ago. Car runs great after it starts, in fact I think the old pump was very weak before it died as I had very poor performance and some drive-ability issues I was tracking that have cleared up with the new pump.
Thank you in advance for any ideas.
#2
AudiWorld Senior Member
Is it hard starting when the engine is cold, say overnight? Or, after driving it and it is warm? Or always? What does hard starting mean? Do you have to crank it for more than a couple seconds? Or, do you have to cycle the key multiple times? Do you touch the gas peddle at all when you try to start it? Or, do you mean it starts and stumbles and you need to play with the gas peddle to keep it running? You need to provide more specific details.
I would guess that all the connections to the pump were done correctly and that you have a second issue. Not a guaranty but a likely. Could be the coolant temp sensor, or it could be your injectors are leaking and flooding the cylinder, or that the fuel pressure is draining off, not into the cylinder but back toward the tank.
I would guess that all the connections to the pump were done correctly and that you have a second issue. Not a guaranty but a likely. Could be the coolant temp sensor, or it could be your injectors are leaking and flooding the cylinder, or that the fuel pressure is draining off, not into the cylinder but back toward the tank.
#3
Thank you for the reply. The hard start is during a cold start. The engine has to crank quite awhile (several seconds) before it fires, it does seem to be getting a bit worse where I stop cranking then crank again and it will generally fire right away on the second turn of the key.
Your last suggestion of the fuel pressure draining off is where my thoughts were headed. Now that I think about it when I was troubleshooting the fuel pump failure I had pulled the fuel lines to check for fuel pressure. I will have to double check those connections are airtight. This condition did not happen before the fuel pump died so I think I introduced it somehow in the troubleshooting.
I will work on it some on Monday when I back by the vehicle. Thank you again. Keep the ideas coming.
Your last suggestion of the fuel pressure draining off is where my thoughts were headed. Now that I think about it when I was troubleshooting the fuel pump failure I had pulled the fuel lines to check for fuel pressure. I will have to double check those connections are airtight. This condition did not happen before the fuel pump died so I think I introduced it somehow in the troubleshooting.
I will work on it some on Monday when I back by the vehicle. Thank you again. Keep the ideas coming.
#4
AudiWorld Senior Member
You might try turning the key to on but not engage the starter, wait a few seconds, turn it off, then on again without engaging the starter, then finally start it. If working correctly, the fuel pump comes on each time you turn the key, assuming it needs to charge the system. If the fuel pressure is draining back toward the tank this will charge the system. If this works there is a pressure holding or anti drain valve that has given up. The system is supposed to hold pressure even when the car is not started for a few days so it will start easily the first time you turn the key. You can drop the back seat and lift the carpet and remove the fuel pump top cover but not access the open fuel tank and hold your hand on the top where the pump is, then have someone do this turn the key without starting routine and see if the pump comes on for a second or so.
#5
Clancy - thank you. That idea of turning the key to prime the system and then turning it again to start it has worked very well to start the car with minimal cranking. I've noticed that the pressure bleeds off fairly quick. Last night at the grocery store, gone for maybe 20 minutes and it had to crank a bit to start. I've not touched the pedal at all, ever for starting.
I'm curious as to what I did in the fuel pump troubleshooting and installation that would have introduced this problem. I'll poke around tonight and see if any clamps are loose.
I'm curious as to what I did in the fuel pump troubleshooting and installation that would have introduced this problem. I'll poke around tonight and see if any clamps are loose.
#6
AudiWorld Senior Member
Possibly just a new pump with better pressure caused a failure in the part that was marginal. Not your fault, just a result of a new pump downline.
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