Fuel pressure gauge question (1 Viewer)

[Tredwards]

Ok y'all,
Trying to track down a fuel pressure issue. Vehicle is a 1996 landcruiser with 1fzfe. How do y'all check system. I am assuming you can get an adapter to fit where the fuel pressure regulator is. Slee on one thread hooked in after fuel filter and did not mess with the FPR. This is probably the best option as it allows you to test the FPR as the FSM recommends with pinching the return line. Is there a special banjo bolt to do this? Was looking at the $80 OTC fuel pressure testing kit on Amazon but not sure if this will work. Actron has one too with a banjo bolt that may work. Any suggestions.

The issue I am having is hard starts after car sits 30-90 minutes after run. Recently did p0401 work, cleaned injectors, replaced FPR, replaced VSV, replaced all vacuum lines, replaced fuel filter and all soft fuel lines. Also replaced charcoal canister as well. Pulled plugs and no carbon deposits and all look clean. Not sure what is going on. Any help would be greatly appreciated.

Thanks,
Tredwards

 

[SUMMIT CRUISERS]

I rented a fuel pressure gauge set for free from Autozone. They charge you for it and then when you return it they credit you. I'm not familiar with where to perform the test on 96 1FZ. On our 92 (3FE) we had a similar problem and it turned out to be the fuel damper. The fuel damper acts as a check valve that holds the pressure in the fuel rail. Does the 1FZ have a fuel damper?

 

[elhombre]

Did your CEL go away after all the work you did? Does the hard start issue occur in the morning when the engine is completely cold also? Or just when it is warm from running around during the day?


You do need that fancy banjo fitting to check the fuel pressure.

 

[Tredwards]

No damper that i could find or see in the FSM. Did put on a new fuel pressure regulator though. The issue does not occur on cold starts, just warm starts after car has been run then sat for 30min - 2 hrs. If i start immediately after turning off it will run fine. When I am driving it does great and no power loss. It will take longer to turn over and then will do a slight stumble on startup. I had a shop do a fuel pressure leak down when they fixed my a/c and they said it was fine, but not sure how they did this, or if they attached to banjo bolt. I pulled spark plugs to look/smell for leak in injectors after applying power to the fuel pump with the battery and pressurizing the fuel system - but did not smell any gas in cylinder and spark plugs look normal without carbon deposit. No external leaks either that i can see or smell. Seems like it has a small fuel leak but not sure. They CEL has not returned after work so far but have not driven much. Did not smell fuel in oil when pulled out dipstick but kinda hard to evaluate this. Not really sure here. Talked to the local guy who cleaned injectors - he said I can run back by to get evaluated but don't want to have to pull intake if don't have to. I would predict if i had a leaking banjo on the fuel filter or rail i would smell gas, if the new lines were leaking i should smell gas as well. Thanks for the help. Greatly appreciate it. Probably will get actron setup as has banjo bolt tester.

 

[elhombre]

I would suggest that you call the shop that did the leak down test and ask them in an open ended question like "Can you explain to me what exactly you had to do to test the fuel pressure?" That should tell you something about their results.

I don't think you have a stuck injector either. Usually a stuck open injector will dump tons of fuel and heat up the catalytic converters so much that you can smell them burning along with a gas smell.

Looking back to your first post, the P401 code is an EGR problem. You may have a torn up EGR diaphragm or stuck open valve. There is a pretty simple test for the EGR modulator and valve in the FSM to check it. Page ENG-123. You will need a vacuum pump set up, but Harbor Freight has a hand one cheap. The EGR system acts differently depending on the temperature of the engine, so it may explain why you have different behaviors at morning start up.

 

[Tredwards]

Ok heres the findings:
Fuel Pressure (taken using banjo bolt with schrader valve adapter at outflow fuel filter fitting)
When cranking - 40 psi
When idling - 30 psi
when FPR return line clamped - 44 psi
when vehicle turned off - 30 psi - then increases to around 35-40 psi
when sitting for 15 min - 25 psi
when sitting 1 hr - 10 psi

Thoughts - appears my fuel pressure is a little on low side - as FSM says should have fuel pressure around 57 when clamp FPR return line. Do appear to have a dropping fuel pressure when sitting - is this possibly a faulty check valve in fuel filter (this is what a mechanic friend thought) - how much pressure should I maintain when sitting? Does it appear I need a new fuel pump? do you think the drop in pressure could be a leaking fuel injector - even though no issues when pulled spark plugs.

Interesting findings - if I bleed off fuel pressure using pressure gauge and drop psi to 0 - vehicle still starts up fine. NO problems with cranking. Fuel pump pumps immediately up to 40 psi and car cranks in 3 clicks of starter.

Also put a vacuum gauge on the egr modulator to valve connection - not pulling any vaccuum when temp on coolant up - and should atleast pull a low vacuum per the fsm. Possibly a bad egr modulator or valve. Have a new VSV so is unlikely this - what do yall think?

Thanks alot for your help. Greatly appreciate it - this is driving me crazy (as well as the wife!)

 

[Tredwards]

It looks like on Slee's post https://forum.ih8mud.com/threads/fu...-manifold-pressure-here-is-the-skinny.278665/ when he jumped the relay the psi with full power to pump was 40 psi. This is fitting with mine at startup. My idling psi is lower than his, his was 37.5. Also my pressure when the FPR vacuum hose is disconnected is 40 psi and Slee's was 45 so still a little low. The main issues I see are that my fuel pressure is low at idle when vacuum hooked up (30 psi) and my fuel pressure is also low when FPR return line clamped (44 and should be 57 per FSM). I'm assuming likely have a new fuel pump, egr valve/modulator in my future.

The only other thing that was done during P0401 work with the EGR system was that the small flow through tube in the intake (between the VSV and the EGR modulator) was bypassed as it was totally rusted through). Could this have possibly caused issues - likely not working prior to this.

Thanks again for helping this semi-noob

 

[Tredwards]

Last thing for tonight. I checked egr valve and it seems functional. The modulator however does not seem to function. The P port polls vacuum when engine is given gas, but the R port does not pull vacuum. is this normal? Thanks ELHOMBRE AND SUMMIT CRUISERS for the help

 

[Tredwards]

Ok here the update. replaced fuel pump - much better. replaced egr modulator and egr valve. When performing FSM checks now still do not get low or high pressure when testing EGR modulator. Things replaced with EGR system: VSV, vacuum hoses, EGR valve, EGR modulator, made sure P/R/E ports on throttle body clean/open. I am getting pressure on R and E ports on throttle body that seems appropriate when testing independently. It appears that the EGR valve is working as when I plug to intake vacuum the car stalls. I believe the vsv is working as when tested has correct Ohms and appears to function when jumping to battery (can't blow air through but can when not jumped).

Heres the problem: When I try to do the FSM testing for the EGR modulator with inline vacuum gauge - I do not see any significant movement from 0 psi. none when throttled up to 2500-3500 rpm with temp above 127 deg, when i should have low vacuum. Not sure what is going on. The P and R hoses independently pull vacuum but when hooked to the egr modulator with inline vacuum gauge - maybe 1 psi. If plug R vacuum hose into intake as FSM says still only 1 psi, when i should have high vacuum. Any help would be great. I'm at a loss.

 

[Tredwards]

Just to make sure I am right. From my reading - random online sources say toyota says that a fuel pressure leakdown test is abnormal when the fuel pressure drops from normal to below 21 in less than 5 minutes, and is fine if it takes longer than 5 minutes. I have read that this is a fairly accurate test for leaks, bad check valves, and faulty injectors that are leaking. Is this correct?

 

[elhombre]

The check valve in the system is to keep the engine from excessive cranking at startup. Seeing how you changed the pump, and it cranks up right away, I would think you are good on the supply side. Have you rechecked your pressures? I 'm curious what you have now at idle and with the vacuumm hose closed off.

Here is some light reading if you haven't come across it yet for fuel systems http://www.autoshop101.com/forms/h42.pdf

Is it still hard to start as you described in the first post, and also, do you still have the 401 code? I'm going to guess you have found this, but just in case https://forum.ih8mud.com/threads/egr-problem.12498/

 

[Tredwards]

Pressures are better. Granted pressure is run off back end of fuel filter and not rail but here's pressures.
1) idling fuel pressure with FPR return hooked up is 32
2) idling fuel pressure without FPR return hooked up is 40
3) idling fuel pressure with return hose clamped 56-58 (much better)
4) fuel pressure takes 25 min to drop to 21 when car shut off (much more slowly than previously)
5) relay seems to work as pressure varies with load on engine

Thanks for the reading I will look over. Egr stuff is driving me crazy, haha. I am leaning towards this at this time or something with efi relay (but would think would be a no start with this instead of a sluggish start)

Really appreciate the advice ELHOMBRE

 

[Tredwards]

Tested the egr system. Egr VSV and fuel VSV ohms correctly and functions correctly with battery power to terminals. Vcv seems to function appropriately as well. TVV seems to function correctly. All ports on throttle body pull vacuum. Have a new egr VSV, new egr valve, new egr modulator. Cleaned passages. Problem is, still no vacuum on gauge when between egr modulator and egr valve. No clue why. FSM says should see a vacuum.

Good thing is runs great, still some startup issues though. Put in new efi relay. Holding fuel pressure above 21 for 25 min after shutoff system. Will eventually drop to zero but I think this is normal?? Oh well. Any other thoughts?

 

[Tredwards]

Ok, Well after working last night on the vacuum system. I finally got it started and it is still doing hard starts after sitting. Here's a video of this - let me know what you think. Hopefully this will give us some ideas - I on the other hand am stumped. Talked with a mechanic - There is still some concern for possibly a leaking fuel injector. Pulled throttle body/intake/fuel injectors and will take back to get rechecked for leaking and flow.Will keep yall updated.

 

[ppc]

I would not call that hard starting. It appeared to be only slightly longer than two seconds that it was cranking. My 94 has been similar to that all it's life when first starting after a similar waiting time.

 

[Tredwards]

Ok here's the update. Took the injectors to get rechecked - appears one was leaking. Called Beno (thanks man) - 6 new injectors ordered and are now put in. Figure they have 280k miles on them. Have been driving the vehicle for 1 week. No issues. Retested fuel pressure and takes much longer to drop now. Readings will go up to around 40 with hot engine and car shutoff, 32 if just a quick start. Neat thing now is that the fuel pressure does not drop below 30 within the first 25-30 min. If I check pressure up to 12 hrs later will only drop to about 5 or 10, not to 0 like before. Also no more issues with starting after sitting for 1-2 hrs. Will crank just fine. MPG in range of 12-15. Runs great. Have put about 200 mi on it so far and no issues. Will keep a watch. Thanks for all yall's help. Appreciate it. Glad this saga is hopefully over. Atleast I have an essentially new fuel system, though the wife is mad at how many hours were spent on it. haha.

 

[elhombre]

Congrats and thanks for the follow up. Has your P401 code gone away too? Do you think there were two seperate problems, meaning that a leaky injector can cause a P401 code also? Do you have any other revelations on how you may have trouble shot the problem more effectively? Just trying to learn more.....

 

[Tredwards]

P0401 appears to likely have been a prior issue. I did have a rusted passageway going from VSV to EGR valve and this may have been part of the issue. P0401 is gone at so far - replaced a ton of stuff but feel better knowing is new. I bought a mityvac to use for testing along with a vacuum pressure gauge and Innova multimeter. This was awesome and made testing EGR components, etc easy. Would recommend these things, got all from Amazon. I used the testing recommendations noted previously in the "vsv the easy way" post about checking the VSV (did this for fuel and egr vsv's). FSM was very helpful.

For the fuel injector issues - I believe this may have occured after having cleaned. I went to a reputable local cleaner who specializes in high end sports cars here in town - he has a 1400RWHp Viper and a Shelby Cobra, AWESOME. Not sure but I believe the issue arose after the cleaning. Oh well. The fuel pressure testing really was beneficial but I did not know the initial norms. My findings currently show fuel pressures coming off the rear of the fuel filter being 32 running, 40-42 with vacuum unhooked on FPR, and 54-56 when fuel return line on FPR clamped. Pressures drop very slowly with all new injectors and drop from 32 or so to 28-30 after 21 minutes. Previously they would drop to low 20's after 21 min. Then after sitting for 1-1.5 hrs my fuel pressures now drop to 20-25 or so where previously they would drop to around 5-10. So big difference here. If i knew these normal's i would have suspected fuel injector sooner. The information I found online made me believe that fuel pressure should stay above 21 for 5 min after car shut off - but my findings are much higher than this. I have found that the pump raises pressure very quickly so a pressure at 0 when starting is not the issue, My issue was that the small leak (2-3drops/min - fsm states should be <1 drop/min) was causing a drop in fuel pressure, flooding of a cylinder, and the hard start issue. Therefore if someone has future concerns for a leaking injector - if it is a small leak you may not note if remove spark plugs and smell for fuel - only may note if doing fuel pressure testing. My definitive test was to have them again flow tested at injector service place and leak down test done noting leak.

Tips I have learned from doing this work. If you remove the throttle body but don't have to clean it - just unbolt and set to side - those cables will drive you crazy. I hate doing the TPS adjustment. The intake can be removed fairly quickly by 1)getting all the bolts on front of intake (near radiator in front of brace) from top of truck, getting front bolt on back half of intake from above, getting next rearward bolt from directly below under truck, and getting last 2 bolts on back/inside of intake from rear of wheel-well opening using a wobble socket. This made this much easier than my first try and I have done this atleast 4 times now. The brace bolt is hard to get back in - had a 200 lb guy pulling down intake to get to thread back in. I wrapped the wiring with heat tape from Amazon as well.

All in all I am glad I did this job. Love being able to work on the Landcruiser on my own and learning - however wish it hadn't taken so long to fix. Wife got a little frustrated with it for sure, however she loves riding it now - we take 30 min-1hr joyrides on weekends around town. No i need to get the ARB, OME 2.5 heavies, and Slee rear dual swing out, and 33's. Still trying to decide on which 33's. BFG A/T, M/T or Duratrac's etc.

Thanks for all your help. Especially Elhombre, Beno, Summitcruisers. Helped alot when I wanted to take the cruiser out and burn it to the ground at times.

 

[702FZJ80]

All ports on throttle body pull vacuum.

Question for you, is this at cold start or when warm? Because my PCV valve port on the manifold is pulling around 16lbs of vacuum but the egr modulator ports are not pulling any that I can tell. This is cold start at idle.

 

[Tredwards]

Both, they won't pull vacuum unless you open throttle. You have to give it some gas, the throttle plate when closed prevents having vaccuum, will pull a vaccuum on all 3 when you give it gas no matter of what temp engine is if I remember correctly