mat in tn Posted March 25, 2022 Share Posted March 25, 2022 Pressure test: Slowly went up to a high of 28psi, while idling, rev it up a bit and went down to 20 and stayed. Turned engine off and pressure slowly going down from 20, Now after 10 minutes off sitting at about 10 psi. No visible fuel leaks from inline pump and filters. I think we should be at around 40 psi? So? two things. identifying the firing order is good. there is no wiring plugged into the iac. is that on purpose? good call on checking fuel pressure. yes, the fuel pressure should be up to 40-45 psi with the engine off. prove that is capable by jumping the fuel pump relay to cause the pump to run constant for 10-15 seconds. plan b would be to cycle the key slowly 5-6 times to give the pump a chance to "stack" fuel pressure. if it gets up to spec then you probably need a new fuel filter. start with regular maintenance and neglected maintenance before condemning hard parts. especially ones which can cause pump failure. Link to comment Share on other sites More sharing options...
mat in tn Posted March 25, 2022 Share Posted March 25, 2022 two things. identifying the firing order is good. there is no wiring plugged into the iac. is that on purpose? good call on checking fuel pressure. yes, the fuel pressure should be up to 40-45 psi with the engine off. prove that is capable by jumping the fuel pump relay to cause the pump to run constant for 10-15 seconds. plan b would be to cycle the key slowly 5-6 times to give the pump a chance to "stack" fuel pressure. if it gets up to spec then you probably need a new fuel filter. start with regular maintenance and neglected maintenance before condemning hard parts. especially ones which can cause pump failure. re reading (I tend to review) i noticed you said the pressure goes down after shutting the engine off. at what pressure does it stop, or does it go to zero? Link to comment Share on other sites More sharing options...
El Chapo Posted March 25, 2022 Author Share Posted March 25, 2022 two things. identifying the firing order is good. there is no wiring plugged into the iac. is that on purpose? good call on checking fuel pressure. yes, the fuel pressure should be up to 40-45 psi with the engine off. prove that is capable by jumping the fuel pump relay to cause the pump to run constant for 10-15 seconds. plan b would be to cycle the key slowly 5-6 times to give the pump a chance to "stack" fuel pressure. if it gets up to spec then you probably need a new fuel filter. start with regular maintenance and neglected maintenance before condemning hard parts. especially ones which can cause pump failure. Yes unplugged it for picture I sent. checked pressure after 40 minutes and down to zero. I tried cycling the key several times to stack fuel, hear pump but no stacking past 10 psi. Started up but then died, I remember only adding like 3 or 4 gallons of gas after I installed new tank, fuel lines, pumps and filters so I’ll add more fuel and new gas cap since I noticed the cap seal was cracked. So maybe not enough fuel in the tank and bad gas cap. I’ll fix that. Link to comment Share on other sites More sharing options...
mat in tn Posted March 25, 2022 Share Posted March 25, 2022 Yes unplugged it for picture I sent. checked pressure after 40 minutes and down to zero. I tried cycling the key several times to stack fuel, hear pump but no stacking past 10 psi. Started up but then died, I remember only adding like 3 or 4 gallons of gas after I installed new tank, fuel lines, pumps and filters so I’ll add more fuel and new gas cap since I noticed the cap seal was cracked. So maybe not enough fuel in the tank and bad gas cap. I’ll fix that. yes, get some fuel in it. don't let that be what derails you. and get used to buying gas. after that if you still have the same then two things are next in line diagnostically. fuel pressure regulator allowing pressure to bleed back too much. and the chance of a leaking injector/s bleeding off pressure into a cylinder. the crazy thing is things always seem to work in threes. when in the air cond. business, it was often three blower motors or three stuck txv or three neglected, filthy systems in a row. this week I have had three different conversations about these same symptoms and giving similar results but three different understandings of the symptoms. one is my son and his modified 92 5.0. the cool thing is he went ahead and installed a pressure gauge permanently where you would normally screw on the tester and while he had the upper removed, he did the fuel pressure reg also. the results are that it runs a little better, but he now can shut the truck off and watch the rail pressure slowly drop to zero. he is now going to be pulling plugs to see if he can determine which injector/s are leaking Link to comment Share on other sites More sharing options...
El Chapo Posted March 25, 2022 Author Share Posted March 25, 2022 yes, get some fuel in it. don't let that be what derails you. and get used to buying gas. after that if you still have the same then two things are next in line diagnostically. fuel pressure regulator allowing pressure to bleed back too much. and the chance of a leaking injector/s bleeding off pressure into a cylinder. the crazy thing is things always seem to work in threes. when in the air cond. business, it was often three blower motors or three stuck txv or three neglected, filthy systems in a row. this week I have had three different conversations about these same symptoms and giving similar results but three different understandings of the symptoms. one is my son and his modified 92 5.0. the cool thing is he went ahead and installed a pressure gauge permanently where you would normally screw on the tester and while he had the upper removed, he did the fuel pressure reg also. the results are that it runs a little better, but he now can shut the truck off and watch the rail pressure slowly drop to zero. he is now going to be pulling plugs to see if he can determine which injector/s are leaking Yup always in three’s I like what your son did that’s a good I idea maybe I’ll do the same. Well the fuel helped I cycled the key and watched it go up to 38psi !! Started up and held! But it’s still dropping pressure when off. So yeah more digging. At least pressure pump is doing it’s job. Ordered a new gas cap.. had a locking cam style cap so my local Napa guy is bringing one in for me. PS: I rebuilt the injectors new o rings, micro filters and checked them with a noid light all checked out fine. Link to comment Share on other sites More sharing options...
mat in tn Posted March 26, 2022 Share Posted March 26, 2022 Yup always in three’s I like what your son did that’s a good I idea maybe I’ll do the same. Well the fuel helped I cycled the key and watched it go up to 38psi !! Started up and held! But it’s still dropping pressure when off. So yeah more digging. At least pressure pump is doing it’s job. Ordered a new gas cap.. had a locking cam style cap so my local Napa guy is bringing one in for me. PS: I rebuilt the injectors new o rings, micro filters and checked them with a noid light all checked out fine. but ..... did you check them operationally under pressure? Link to comment Share on other sites More sharing options...
El Chapo Posted March 26, 2022 Author Share Posted March 26, 2022 but ..... did you check them operationally under pressure? Kinda when rebuilding as a test I hooked them up a makeshift Tire valve and a can of starter fluid to the intake side and briefly hit them with 12 volts. (YouTube hack) and they worked fine that way Link to comment Share on other sites More sharing options...
El Chapo Posted March 26, 2022 Author Share Posted March 26, 2022 Kinda when rebuilding as a test I hooked them up a makeshift Tire valve and a can of starter fluid to the intake side and briefly hit them with 12 volts. (YouTube hack) and they worked fine that way Put like your son’s situation them could be leaking on the rail or manifold Link to comment Share on other sites More sharing options...
mat in tn Posted March 26, 2022 Share Posted March 26, 2022 Put like your son’s situation them could be leaking on the rail or manifold my concern is the injectors' ability to seal and hold back pressure. not its ability to open. this type of leak will not spill out in a visible area. and if pressure is able to bleed off to zero in under 20 minutes as in his case, then a puddle of fuel will eventually end up on the piston and over a short period weep down past washing any oil from the areas requiring oil and diluting the oil with a solvent. a flammable one! yes, if this condition is found an oil change is a must. Link to comment Share on other sites More sharing options...
El Chapo Posted March 27, 2022 Author Share Posted March 27, 2022 my concern is the injectors' ability to seal and hold back pressure. not its ability to open. this type of leak will not spill out in a visible area. and if pressure is able to bleed off to zero in under 20 minutes as in his case, then a puddle of fuel will eventually end up on the piston and over a short period weep down past washing any oil from the areas requiring oil and diluting the oil with a solvent. a flammable one! yes, if this condition is found an oil change is a must. Thx Mat, I assume that explains the tailpipe carbon spit and smoke? I’ll change the oil asap, and get all new injectors making sure that they are properly lubricated and sealed, I’ll inspect the fuel rail itself especially the rear tubing section that connects the right and left side on the rail. Is this a good approach? Not doing the cheapo Amazon injector but ones from Napa.? Link to comment Share on other sites More sharing options...
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