No fuel pressure...

[1991MJPioneer]

Well I tried starting my stroker tonight... It seems that everything is functioning but I'm just not getting good fuel pressure to the fuel rail. Fuel pump is working and is pumping fuel. It is noisy though. It was just as noisy as when it ran last summer.

 

Tonight when I cranked it over, it fired a few times and then started spraying fuel from the pressure regulator on the fuel rail. I went to the parts store and bought a new o ring...it stopped leaking, but now its not firing at all. Good spark as far as I can tell. Engine malfunction lamp is blinking also...

 

Could my problem be partially because I don't have the oxygen sensor hooked up along with the coolant temp sensors?

 

I don't really know where to start. Could my fuel strainer sock be plugged up? the truck has been sitting since last June.

[Wildman]

First question.........You have fresh fuel???

 

Your not trying to start this with the fuel in the tank from last June......are you :eek:

 

Can you do a pressure check at the test valve??? This would lead to checking the fuel tank if needed, if the sock strainer is plugged, or the soft fuel line in the tank is bad/unhooked. Or a bad fuel pump. You wrote it is noisy.

 

Assuming that you have the distributor set correctly, and not 180* off, which is easy to do, or even one tooth off.

 

Having the o2 sensor unhooked would only keep the engine running in open loop, it would still start. Having the temp sensor unhooked would not have any effect on the engine starting, it just adjusts the fuel/air mixture after the engine warms up.

 

Check all that.......and let us know what you find ;)

[ratrapp]

the o2 sensor won't hurt but leaving the coolant temp sensor unhooked can cause it to deliver too much or not enough fuel.

[1991MJPioneer]

First question.........You have fresh fuel???

 

Your not trying to start this with the fuel in the tank from last June......are you :eek:

 

Can you do a pressure check at the test valve??? This would lead to checking the fuel tank if needed, if the sock strainer is plugged, or the soft fuel line in the tank is bad/unhooked. Or a bad fuel pump. You wrote it is noisy.

 

Assuming that you have the distributor set correctly, and not 180* off, which is easy to do, or even one tooth off.

 

Having the o2 sensor unhooked would only keep the engine running in open loop, it would still start. Having the temp sensor unhooked would not have any effect on the engine starting, it just adjusts the fuel/air mixture after the engine warms up.

 

Check all that.......and let us know what you find ;)

 

 

Actually... :roll: yeah the fuel in the tank is from last June. I just wanted to see it start and then I was gonna put fresh gas in it afterwards if everything worked.

 

I did a check at the test valve and it showed me nothing yesterday but I'll mess with it again.

 

I'm not 100% positive that the dist is set properly, I thought I set it properly before I put the motor in.

 

As for the dist...it may be one tooth off...its pointing in the right direction and its set at number one end of compression stroke. :hmm:

[1991MJPioneer]

Yep definitely no fuel pressure at all. I checked with gauge. Also depressed valve on rail with screwdriver and it just hisses and bubbles. I disconnected fuel return line and a little fuel came out but not much. I poured a little fuel into the intake and it fires right away. I haven't checked the timing again yet...but I thought I'd start with the fuel problem.

 

I'm gonna take the fuel pump out and check everything.

[Wildman]

If the dizzy is setting at #1 at TDC on the compression stroke, you should be good there :D

 

It's really easy to get it off one tooth, as it drops in.

 

Yea, stale gas is :no: But you understand that.

 

Pull the sending unit out, and check out the tank/pump. And a new fuel filter to see what happens then ;)

 

I'll agree with ratrapp to hook the temp sensor back up, this could cause idle problem even in the open loop, cold start.

 

Oh......did you check the ballast resistor??? That will also cause the pump to run loud, or non running fuel pump.

[1991MJPioneer]

So today I took the fuel pump/sender unit out of the tank and to my suprise....there was no strainer sock on the fuel pump... :dunno: I tried looking down in the tank and it looked relatively clean for a 20 year old truck...but couldnt see if the strainer had fallen off somehow. Could the strainer possibly fallen off in the process or removing the pump?

 

I tested the pump briefly while it was out of the truck and it pumps...but I don't know the proper procedure for testing it

 

Anybody?

[Oizarod115]

So today I took the fuel pump/sender unit out of the tank and to my suprise....there was no strainer sock on the fuel pump... :dunno: I tried looking down in the tank and it looked relatively clean for a 20 year old truck...but couldnt see if the strainer had fallen off somehow. Could the strainer possibly fallen off in the process or removing the pump?

 

I tested the pump briefly while it was out of the truck and it pumps...but I don't know the proper procedure for testing it

 

Anybody?

you said you replaced an o-ring at the fuel rail, any way you accidently got something inthere an plugged it up? like the old o-ring perhaps?

[1991MJPioneer]

So today I took the fuel pump/sender unit out of the tank and to my suprise....there was no strainer sock on the fuel pump... :dunno: I tried looking down in the tank and it looked relatively clean for a 20 year old truck...but couldnt see if the strainer had fallen off somehow. Could the strainer possibly fallen off in the process or removing the pump?

 

I tested the pump briefly while it was out of the truck and it pumps...but I don't know the proper procedure for testing it

 

Anybody?

you said you replaced an o-ring at the fuel rail, any way you accidently got something inthere an plugged it up? like the old o-ring perhaps?

 

 

Doubt it. I threw the old o-ring away. I had the no pressure problem the first time I tried starting the truck.

[Eagle]

Could my problem be partially because I don't have the oxygen sensor hooked up along with the coolant temp sensors?

How do you expect it to run if you don't have the engine control sensors connected?

[Oizarod115]

Could my problem be partially because I don't have the oxygen sensor hooked up along with the coolant temp sensors?

How do you expect it to run if you don't have the engine control sensors connected?

:smart: :rotfl2:

[1991MJPioneer]

Could my problem be partially because I don't have the oxygen sensor hooked up along with the coolant temp sensors?

How do you expect it to run if you don't have the engine control sensors connected?

:smart: :rotfl2:

 

Yeah I know it won't run all too well without all sensors hooked up. I know the engine fires...I'm not worried about it running perfect right now. I just am trying to figure out the fuel pump issue so I can have fuel pressure. :???:

[1991MJPioneer]

Just wanted to know if the pump strainer could've fallen into the tank. It wasnt there when I removed the pump. Thought I'd ask here tho since I'm kind of a noob when it comes to some stuff. ;)

[HOrnbrod]

On an HO, the O2 and temp sensors disconnected will not affect starting; it'll just stay in open loop but should start. I think the stale fuel is the problem and may have clogged/gummed up your fuel lines, since your pump sounds like it's working out of the vehicle (ASSume you are pumping from a bucket of clean fuel into another container). Blow compressed air into the fuel supply line from the fuel tank w. the fuel filter removed until cleared, then do the same from the filter to the fuel rail w. the supply line disconnected. Then do the same with the return side as they will vapor lock w/o a clear return to the fuel tank.

[Wildman]

The sock filter should be on the fuel pump, in the tank, it could have fallen off when you pulled the sending unit out, if you have really skinny arms, see if you can reach in the tank and find it.

 

If the truck was running with out the sock filter, that could be a problem, no mater how clean the inside of the tank looks.......there is still debris present.

 

Mr. Hornbrod brings up a very good tip for you. Your at the point that you should clean out the fuel lines, and replace ALL filters.

 

The problem you might have now, and lets not hope it's that bad........but, any crud in the fuel lines are not nice to the injectors :eek:

 

6 month old gas is varnish, the injectors don't squirt varnish.......get where I'm going here.

 

Clean out the lines, replace the filters, and with fresh gas, see if you have any pressure at the fuel rail. Oh, and don't be afraid to add some injector cleaner to the fresh gas.

[1991MJPioneer]

On an HO, the O2 and temp sensors disconnected will not affect starting; it'll just stay in open loop but should start. I think the stale fuel is the problem and may have clogged/gummed up your fuel lines, since your pump sounds like it's working out of the vehicle (ASSume you are pumping from a bucket of clean fuel into another container). Blow compressed air into the fuel supply line from the fuel tank w. the fuel filter removed until cleared, then do the same from the filter to the fuel rail w. the supply line disconnected. Then do the same with the return side as they will vapor lock w/o a clear return to the fuel tank.

The sock filter should be on the fuel pump, in the tank, it could have fallen off when you pulled the sending unit out, if you have really skinny arms, see if you can reach in the tank and find it.

 

If the truck was running with out the sock filter, that could be a problem, no mater how clean the inside of the tank looks.......there is still debris present.

 

Mr. Hornbrod brings up a very good tip for you. Your at the point that you should clean out the fuel lines, and replace ALL filters.

 

The problem you might have now, and lets not hope it's that bad........but, any crud in the fuel lines are not nice to the injectors :eek:

 

6 month old gas is varnish, the injectors don't squirt varnish.......get where I'm going here.

 

Clean out the lines, replace the filters, and with fresh gas, see if you have any pressure at the fuel rail. Oh, and don't be afraid to add some injector cleaner to the fresh gas.

 

 

Ok. Good news. I have fuel pressure finally and the engine idles. I set the pump in a bucket of fresh gas and pumped directly to the rail bypassing the old fuel filter. It took a good few times to prime the system and for it to hold pressure, but it shows me about 35-37 PSI while running. As of right now, the pump is holding at about 30 PSI with engine off. It might still be dropping as thats what it was doing.

 

I would hope this means that I have a useable pump. The engine cuts out if I attempt to rev it. I suppose this is because the oxygen sensor and coolant temp sensor arent hooked up and it is in open loop. Right?

 

Thanks for the help ;)

[HOrnbrod]

Ok. Good news. I have fuel pressure finally and the engine idles. I set the pump in a bucket of fresh gas and pumped directly to the rail bypassing the old fuel filter. It took a good few times to prime the system and for it to hold pressure, but it shows me about 35-37 PSI while running. As of right now, the pump is holding at about 30 PSI with engine off. It might still be dropping as thats what it was doing.

 

I would hope this means that I have a useable pump. The engine cuts out if I attempt to rev it. I suppose this is because the oxygen sensor and coolant temp sensor arent hooked up and it is in open loop. Right?

 

Thanks for the help ;)

 

Good fuel pump? Maybe yes, maybe no. You should do a flow rate test also - you can have good pressure with poor flow especially as long as it's been setting. Poor flow could be why the engine is cutting off, or gummed up injectors. It should not be cutting off because the O2 sensor and temp sensor are not hooked up. I think you still have a fuel flow problem. Check this out:

 

http://www.lunghd.com/Tech_Articles/Fuel_System/Fuel_Diagnostics.htm

[Wildman]

:yes: :agree: :yes:

[1991MJPioneer]

Darn...well. I'll get on that flow rate test then. I was considering replacing the injectors with higher flow units anyways at some point. I suppose I could buy new or cleaned up ford 24# injectors somewhere. I'll aslo see if the '91 FSM has anything on testing for flow rate.

[HOrnbrod]

Yes, it's in the FSM. And if you do get new injectors, don't use the Ford 24#, they are way too much for a non-aspirated stock engine. It will run like crap and waste fuel. Use the stock 19#-ers. You will be happier. :cheers:

[1991MJPioneer]

Yes, it's in the FSM. And if you do get new injectors, don't use the Ford 24#, they are way too much for a non-aspirated stock engine. It will run like crap and waste fuel. Use the stock 19#-ers. You will be happier. :cheers:

 

Ok cool. I'll read up on it tonight.

 

What size injectors are you running in your stroker Don? I've read that guys have used the 24# Ford in strokers. Also my concern was that with my stroker, I'll have detonation issues because I'm running a stock cam and 9.7 to 1 compression. I was thinking that the larger injectors might be beneficial.

[HOrnbrod]

Ok cool. I'll read up on it tonight.

 

What size injectors are you running in your stroker Don? I've read that guys have used the 24# Ford in strokers. Also my concern was that with my stroker, I'll have detonation issues because I'm running a stock cam and 9.7 to 1 compression. I was thinking that the larger injectors might be beneficial.

 

My apologies - didn't notice you had a 4.5 stroker. :D I'm using the 96-99 Mopar 23.2lb/hr grey tops, p/n 53030778, and running them at 46psi. These provided the best numbers on the Hesco dyno for my particular setup w. the cam, exhaust/intake mods and Unichip I have. If you frequent the stroker forum or the Hesco forum, there are long discussions regarding optimum stroker injector sizing. Most, but not all, if using the Ford 24# injectors, end up running them at a lower pressure than the stock regulator lets them. You might get by using them on your setup, but only a dyno run (not the olde butt dyno) will let you optimize it. HTH.........

[1991MJPioneer]

Ok cool. I'll read up on it tonight.

 

What size injectors are you running in your stroker Don? I've read that guys have used the 24# Ford in strokers. Also my concern was that with my stroker, I'll have detonation issues because I'm running a stock cam and 9.7 to 1 compression. I was thinking that the larger injectors might be beneficial.

 

My apologies - didn't notice you had a 4.5 stroker. :D I'm using the 96-99 Mopar 23.2lb/hr grey tops, p/n 53030778, and running them at 46psi. These provided the best numbers on the Hesco dyno for my particular setup w. the cam, exhaust/intake mods and Unichip I have. If you frequent the stroker forum or the Hesco forum, there are long discussions regarding optimum stroker injector sizing. Most, but not all, if using the Ford 24# injectors, end up running them at a lower pressure than the stock regulator lets them. You might get by using them on your setup, but only a dyno run (not the olde butt dyno) will let you optimize it. HTH.........

 

 

No problem Don. :cheers: I actually have two sets of the 96-99 grey tops. I bought a 97 block and the guy just gave me two intakes with everything...unfortuneately I don't know what condition they are in.

 

I guess you're running the Hesco Adjustable FPR? and I suppose the guys running the Ford 24# end up with too much fuel if running at stock pressure? is that the later 50 PSI pump or the earlier 39 PSI H.O. pump?

 

Will the factory 21# injectors suffice for now or should I invest my money in a FPR and different injectors?

[HOrnbrod]

I guess you're running the Hesco Adjustable FPR? and I suppose the guys running the Ford 24# end up with too much fuel if running at stock pressure? is that the later 50 PSI pump or the earlier 39 PSI H.O. pump?

 

Will the factory 21# injectors suffice for now or should I invest my money in a FPR and different injectors?

 

I have the stock 91 HO fuel pump and the Hesco HES9195FR adj. FPR. It comes pre-adjusted at 44PSI.

 

I would definitely use the adj. regulator and try the 21# injectors first at the pre-adjusted pressure setting. I think this will be fine for your application. If you need more, you can always swap in a set of the grey tops after having them checked and cleaned, then fine tune the regulator. A good A/F meter is good to get the mixture correct. Here's a little blurb on injector sizing:

 

Stroker engines require oversize injectors to provide adequate fuel flow rates and prevent pinging due to lean air/fuel mixtures.

 

To calculate optimum injector size, use the following formula:

 

Injector flow rate (lb/hr) = [Expected HP x 0.5 (BSFC)] / [no. of cylinders x 0.8 (injector duty cycle)]

 

The actual injector flow rate from each injector depends on the fuel pressure (FP) in the injector rail. Most injectors have rated flows at 43.5psi fuel pressure. The actual flow rate from each injector is:

 

Actual injector flow rate = Rated injector flow rate at 43.5psi x square root of (FP/43.5)

 

This can get you in the ballpark, then hook up an A/F meter to get the mixture correct. :cheers:

[1991MJPioneer]

Well first things first I've gotta test the flow rate of my pump. I definitely don't have the money to buy a pressure regulator or a pump or get injectors cleaned. I'm a poor college student so things will get fixed as I slowly accumulate the money :cheers:

 

Theres a book called Jeep 4X4 Performance Handbook that has those formula's in it. I've seen them too on Jeep Strokers forum.

 

Thank you Don :thumbsup: