Simple Injector Troubleshooting

[coolwind57]

I've been having delayed starting/excessive cranking issues for several Months now and I've slowly been getting around to checking components relating to the issue.  The only thing left that I can think of that may be in the equation are my injectors.

 

You may have seen my wining in other posts already, but here's the scenario:  Most of the time, my engine cranks excessively before starting.  I'm talking more than a few seconds--more like 8-10 seconds at times.  I often stop and crank a second time to get her to fire and I usually always get a puff of strong gas odor & smoke from tail pipe.  

 

The only consistencies I've observed is this:  She fires right up within a second or two if she sits for a day or two (cold).  It's pretty consistent that the excessive cranking problem happens most if I have the engine warmed and shut down and park for a short stop (as in errand running) and try to start the engine again.    This usually always causes an embarrassing amount of time to start.

 

So I've checked, tested, replaced and/or cleaned IAC, MAP, O2, TPS, CPS.  Got a new (bored) throttle body from MeanLemons.  Checked fuel pressure and regulator function (very minor pressure loss after sitting, but I'd always had that gradual drop long before this issue).  New distributor, new 8.2mm Thundervolt plug wires,  Napa Gold distro cap with copper contacts.  Removed and cleaned coil and contacts.  Anyhow, no cigar.  I'm suspecting that one of the injectors is perhaps not shutting off properly, maybe drowning a cylinder after engine shut-off?  Does this sound right?  Perhaps a flooded chamber or two is causing the "flooded-like" conditions--delayed starting/strong gas smell at start.    

 

So is there a way to check proper function of the injectors, preferably while still installed?  The only thing I've done at this point was to remove each individual injector connector at idle and listen for engine rpm drop.  As far as that goes, all caused a very slight drop in engine rpm--i understand that as a good thing. 

 

Any more simple tests that I can try before pulling them and the fuel rail?  I currently have 1-year old 746 Bosch-copy 4-hole injectors.  

[yxmj]

For a simple test while installed I use a Mechanics stethoscope.......just run the motor.... place the end of the scope on the body of the injector....you want to hear a clear clicking noise on all of them......no noise....not working.....a buzzing or rattling noise not good (but the injector might still be functioning) (You can do this with a screwdriver if you do not play doctor)

 

To test ( and clean) injectors from the JY I made a little rig with a plug from an old harness.....a push button switch.....and a 9 volt battery......I take a can of throttle body or carb cleaner....Place the end of a pen body on the straw so it fits the opening of the injector.....now spray a shot into it to pressurize it and push the button.....

[Ωhm]

Hold the throttle wide open and to the floor during CRANK. This condition is known as "clear flood" and shuts off the injectors during CRANK. Quick way to check for leaky injectors.

[bluenotenick]

My MJ does this too sometimes, although it is less of a crank time. More like 4 seconds when warm versus almost immediate when cold. I also have intermittent throttle response issues. On a nice cool night the throttle response is great... linear and normal. When things heat up mid-day in traffic and doing around 45 mph, there is almost no throttle response until I get to around 2/3 throttle and then there is a kick-in with high acceleration.

 

A while back JeepPapa and I cleaned out my single-hole injectors using a method similar to yxmj's (above). I noticed an improvement overall, but my throttle lag and occasional slow crank remains. I did seem to notice some improvement after changing out the fuel filter a couple times, but then symptoms return a day or so after. Hoping we can get to the bottom of this... If not, I might drop my tank at a future date.

 

 

[coolwind57]

1 hour ago, Ωhm said:

Hold the throttle wide open and to the floor during CRANK. This condition is known as "clear flood" and shuts off the injectors during CRANK. Quick way to check for leaky injectors.

So if I see improvement each time I do this, then it means that i likely have an injector or two that's leaking fuel into the chamber, right?

[Ωhm]

2 hours ago, coolwind57 said:

Perhaps a flooded chamber or two is causing the "flooded-like" conditions--delayed starting/strong gas smell at start.

Lets see if any improvement occurs. Something is giving you that 'strong gas smell at start'. Could be no spark.

[HOrnbrod]

4 hours ago, yxmj said:

For a simple test while installed I use a Mechanics stethoscope.......just run the motor.... place the end of the scope on the body of the injector....you want to hear a clear clicking noise on all of them......no noise....not working.....a buzzing or rattling noise not good (but the injector might still be functioning) (You can do this with a screwdriver if you do not play doctor)

 

^^  Thanks for this. Found my long lost stethoscope last week while cleaning the garage. Turns out my granddaughter was using it to listen to the dogs' heartbeat.  

 

All the injectors are happily clicking away and all sound the same. 

[zomeizter]

Check for leaking injectors/fuel pump check valve by performing a fuel pressure drop test. Also, I battled this for a while on a GM vic, turned out to be a defected coolant temperature sensor...$0.02

[cruiser54]

If they are the stock injectors which have a crimp and are prone to leaking fuel, replace them with a refurbished set of Volvo 0 280 155 746 injectors. 

[fiatslug87]

Did you ever resolve this problem?

[coolwind57]

On 12/29/2018 at 11:31 AM, fiatslug87 said:

Did you ever resolve this problem?

Nope.  Not yet.  

 

On 11/3/2018 at 10:29 AM, cruiser54 said:

If they are the stock injectors which have a crimp and are prone to leaking fuel, replace them with a refurbished set of Volvo 0 280 155 746 injectors. 

I had a set of new aftermarket 746 injectors.  I replaced with eBay remanufactured Bosch-brand.  I was certain this would help  But it didn't.  

On 11/2/2018 at 3:01 PM, Ωhm said:

Lets see if any improvement occurs. Something is giving you that 'strong gas smell at start'. Could be no spark.

It helps a little when I hold accelerator down while cranking.  But cranking is still excessive.  

 

I've not figured this one out yet.  I did see a drop in pressure after shutting the engine down last time I rented a fuel pressure tester...but it wasn't an immediate drop.  The drop was over several minutes and didn't seem excessive.  

[cruiser54]

Double check the integrity of the MAP sensor to throttle body vacuum line and fittings.