Rough idle after new injectors?

[ari666]

o2 sensors are an off/on sensor to tell the ecu to make small changes to the fuel map and then make further long term fuel changes if a lean or rich condition is persistant.

MAF, IAT, TPS have no bearing on the O2's reading, its just rich or lean. on or off

i think we have determined that the 2 sets of injectors are different, and thus why he is expierencing issues with the new ones. we have a saying in the auto industy "if it aint broke, then dont fk with it" and i think that saying is very pertinant to this thread.

 

[Kokentoe]

Rather than make a new thread, I've bumped this one as I went and bought some genuine bosch injectors, the same as what originally came with the car. The idle is now normal and everything seems to be running fine after taking it for a drive. There is only one small issue which occurs when starting the car. It will hesitate for a second before turning on, sounding as if it's trying to get fuel. Sometimes it will start without the hesitation. Is this common for new injectors? Will it eventually start up straight away after a given amount of time?

 

[diysv6]

............... There is only one small issue which occurs when starting the car. It will hesitate for a second before turning on, sounding as if it's trying to get fuel. Sometimes it will start without the hesitation. Is this common for new injectors? Will it eventually start up straight away after a given amount of time?

Have you connected a fuel pressure gauge at the access point at the rear of the motor? This would tell you if the car has zero fuel pressure and needs to pump up before applying the starter motor. Maybe your fuel pump is sluggish on start up? The starting logics may require a certain fuel pressure before cranking starts. When you shut down the engine, does the fuel pressure stay up for about 5-10 minutes and slowly reduce? If it drops quickly then one of your injectors may be leaking down. This could give you a rich start and maybe the smell of a rich exhaust discharge.

 

[A9L]

^ Yup, plus given that they all are set to run rich when cold.

 

[Kokentoe]

Well it just so happens I have a Vacuum and Fuel pressure tester. I originally bought solely to check for vacuum leaks so now I must ask, how does one go about checking the fuel pressure? Where about is this access point and do I need to use a special adapter on the end of the hose? There seem to be a couple that came with the gauge. Photos would be helpful but any advice is appreciated. Cheers.

 

[diysv6]

Well it just so happens I have a Vacuum and Fuel pressure tester. I originally bought solely to check for vacuum leaks so now I must ask, how does one go about checking the fuel pressure? Where about is this access point and do I need to use a special adapter on the end of the hose? There seem to be a couple that came with the gauge. Photos would be helpful but any advice is appreciated. Cheers.

Automotive Diagnostic Service Tools Fuel Pressure Injection Testers | eBay

You need a fuel pressure tester with the Schrader valve adapter to connect into the fuel pressure test point.

In this eBay kit I think it is the hose connected to the pressure gauge in the package box.
Does yours have this style of connector? Screw on brass fitting much like a car tyre valve only more robust and maybe larger.

Some of the simpler combo vacuum/pressure gauges have a tapered plastic wedge to push into the fuel/vacuum line. Don't even try to use this type of gauge. You could end up with a fire and high pressure fuel in your eyes.

The access point is at the rear of the inlet manifold and there is a un-screwable black cap which exposes the Schrader valve fitting on the fuel log.

 

[Kokentoe]

Ah yep, I believe I found it. Always wondered what the purpose of that was. It appears I do not have the necessary adapter for the valve. Guess I'll have to buy one from somewhere. So once I have the right piece, do I simply screw it on, then start the car and record the pressure rating?

 

[diysv6]

Ah yep, I believe I found it. Always wondered what the purpose of that was. It appears I do not have the necessary adapter for the valve. Guess I'll have to buy one from somewhere. So once I have the right piece, do I simply screw it on, then start the car and record the pressure rating?

Wear safety glasses, hand protection, have a fire extinguisher handy in event of high pressure fuel fire etc. Keep some rags around to wipe up any spilled fuel.


Alloytec:
I initially removed the fuel pump relay, started the car, it ran out of available fuel after a few seconds. Then removed the plastic cover, wiped away any grit, then screwed the Schrader fitted gauge on.
Reinstalled the fuel pump relay, and started up OK. You should get a reading at idle, check for any leaks as the fuel line runs at 57 lb/sq inch about 400 kPa metric units. (I think spec is 410kPa)
Mine ran 57 psi. Turned off - After 2 minutes was about 42psi. After 14 minutes was 21psi.

Note - I got a DTC about fuel failure from this method - P0627.

If I had a leaking fuel injector I would expect the pressure to drop fairly quickly.

If you have one of these simple dial gauge vacuum/pressure gauges don't even try it.
They only handle 10psi of fuel pump pressure for carbureted motors. Hence no Schrader adapter in the kit.

CAR Tester Manifold Gauge Test Carburetor Valve Fuel Pump Pressure Vacuum | eBay


The VZ keeps the fuel line under pressure until is slowly bleeds down over a period of time. Some cars with the fuel return line to the fuel tank from the fuel log probably allow the fuel line to drop pressure fairly quickly. That may explain that when I had a look around utube, some contributors there hook up the Schrader fitting without depressurizing the fuel line.

 

[Kokentoe]

Cheers mate. I went and ordered a complete fuel pressure test kit which will hopefully arrive tomorrow.

 

[Kokentoe]

I did the test today and I got around 60psi with the car running. The reading went straight down to 56 after turning the car off. Then after 5 minutes it went down to 50psi and after 10 minutes it went down to 45psi. Anyone know what this would indicate?