Keith Browning Posted October 12, 2010 Share Posted October 12, 2010 This is odd, not only for what it is but also because it just hit me after all these years. "We" consider fuel pressure below 45 to generally be bad, the lower the more likely internal injector damage is to occur. So why is the minimum fuel spec for F Series 45 PSI and for the E Series it is only 38 PSI? What is the real threshold for injector damage and what is it about the E Series that makes 38 PSI acceptable? Quote Link to comment Share on other sites More sharing options...
mchan68 Posted October 13, 2010 Share Posted October 13, 2010 What is the real threshold for injector damage and what is it about the E Series that makes 38 PSI acceptable?I guess it's part of the difference in strategies between the two applications. With the E-Series being rated at only 240 BHP/440 ft-lbs. and the F-Series rated at 325 BHP/570 ft-lbs. I would think the F-Series application requires more fueling, hence the higher pressure specs. Just my . Quote Link to comment Share on other sites More sharing options...
GregKneupper Posted October 13, 2010 Share Posted October 13, 2010 The reason the fuel pressure spec is lower on the e series is because it is tested at the back of the cylinder head after the injectors. The injectors firing will lower the fuel pressure in the cylinder head. If you test fuel pressure on an e series at the secondary fuel filter housing it will be higher like the f series. That is the reason for the different specs. Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted October 13, 2010 Author Share Posted October 13, 2010 The reason the fuel pressure spec is lower on the e series is because it is tested at the back of the cylinder head after the injectors. The injectors firing will lower the fuel pressure in the cylinder head. If you test fuel pressure on an e series at the secondary fuel filter housing it will be higher like the f series. That is the reason for the different specs. Excellent theory and one I have not heard explained. Now, did you realize this on your own or did you hear this from a reliable source of sorts? Not doubting you, just curious. Quote Link to comment Share on other sites More sharing options...
Mekanik Posted October 14, 2010 Share Posted October 14, 2010 If you test fuel pressure on an e series at the secondary fuel filter housing it will be higher like the f series. Good luck checking it at the fuel filter housing. Originally Posted By: Keith Browning Excellent theory and one I have not heard explained. Now, did you realize this on your own or did you hear this from a reliable source of sorts? Not doubting you, just curious. I think we covered this here a few years ago. It might explain something very similar in the testing procedure in the PCED. Quote Link to comment Share on other sites More sharing options...
GregKneupper Posted October 14, 2010 Share Posted October 14, 2010 Keith, it is something that I thought of my self. I am pretty sure it is quite accurate as I have been able to check fuel pressure at the filter housing and yes it is a real bitch to do. Quote Link to comment Share on other sites More sharing options...
Mekanik Posted October 14, 2010 Share Posted October 14, 2010 Keith, it is something that I thought of my self. I am pretty sure it is quite accurate as I have been able to check fuel pressure at the filter housing and yes it is a real bitch to do. My hat's off to you. I spent about an hour once TRYING to check fuel pressure at the filter housing. Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted October 14, 2010 Share Posted October 14, 2010 Hang on- IIRC, the PCED says to check FP on an E-van at he secondary FF at the same plug as an F-model, which is a real pain to access. I may have been the one to come up with the rear-of-the-head check. We did cover it several years ago with pics, here is the thread: http://www.forddoctorsdts.com/forums/ubbthreads.php?ubb=showflat&Number=6394&page=1 I think I'd agree with Mike, the lower HP means (probably) lower ICP pressures which means less chance of damaging the injectors if FP falls off. Or, it could be FMC changing things for no reason...... Quote Link to comment Share on other sites More sharing options...
mchan68 Posted October 14, 2010 Share Posted October 14, 2010 I vaguely recall one of my Ford school instructors showing us a spare secondary fuel filter cap with a brass fuel pressure fitting drilled and tapped into it, that could be used specifically for checking fuel pressure on E-Series a few years back. Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted October 14, 2010 Share Posted October 14, 2010 A lot of guys do that on PSD's but I hate it- you're checking FP before the filter, standpipe, and check valves. That's asking for big time trouble if you ask me. Quote Link to comment Share on other sites More sharing options...
Spdracer Posted October 15, 2010 Share Posted October 15, 2010 I've always checked fuel pressure at the fuel pump on the frame. All of the decent fuel pressure test kits have the adaptors to "T" into the quick disconnect line. It's a lot faster and eaiser to do. Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted October 15, 2010 Share Posted October 15, 2010 Chris: Yes, it's easier to do, but you're not getting a true pressure reading there. Like I said in the last post, what if the secondary FF is restricted? What if the standpipe is broken or the check valves on the heads are defective? Why do the test if you can't rely on the results? Quote Link to comment Share on other sites More sharing options...
Spdracer Posted October 15, 2010 Share Posted October 15, 2010 True, but on a driveability concern I always try to get a fuel sample and change the filters anyways. I agree you are not checking the standpipe and maybe a checkvalve failure at the cylinder head. I feel that checking it at the HFCM, changing the filters, getting a fuel sample takes care of 95% of the fuel problems that I have personlally seen. If I have to, I'll get the pressure at the correct location. Quote Link to comment Share on other sites More sharing options...
joshbuys Posted October 15, 2010 Share Posted October 15, 2010 Also checking at the HFCM will not show us if the fuel pressure regulator is working properly. I don't know how many times I've had to put a fuel pressure regulator on a truck to bring the fuel pressure into it's proper spec! Quote Link to comment Share on other sites More sharing options...
GregKneupper Posted October 15, 2010 Share Posted October 15, 2010 Actually if you read the pced it now states to check fuel pressure on an e series at the back of the cylinder head now. Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted October 15, 2010 Share Posted October 15, 2010 Aaahhh, I didn't check the PCED lately. I know before it had us check it at the FF. Quote Link to comment Share on other sites More sharing options...
GregKneupper Posted October 15, 2010 Share Posted October 15, 2010 I believe that it changed when the special fuel pressure tool was released. Quote Link to comment Share on other sites More sharing options...
Mekanik Posted October 16, 2010 Share Posted October 16, 2010 Also checking at the HFCM will not show us if the fuel pressure regulator is working properly. I don't know how many times I've had to put a fuel pressure regulator on a truck to bring the fuel pressure into it's proper spec! More times than not, I'm replacing a regulator with injectors. Quote Link to comment Share on other sites More sharing options...
2006 Posted October 17, 2010 Share Posted October 17, 2010 I also change the regulator along with any injectors even if it falls with specs. The new regulator springs are 2 coils longer. With new filters on a f-series, the pressure is boosted to 70 psi max and about 55 psi min with the new fuel gauge tester. It also helps those lazy injectors... Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted October 17, 2010 Share Posted October 17, 2010 I never check fuel pressure on 6.0ls, I just replace parts til I get the right one. Quote Link to comment Share on other sites More sharing options...
Aaron Posted October 18, 2010 Share Posted October 18, 2010 Working at Rex's shop now, Brad? I like the new regulator kit, however -- don't bother selling it on an E-series... see if you can get the spring seperately from ITEC -- that's the only part of the regulator kit you can use. Seems a little heavy... $112 or whatever it retails at this week for a spring that could be robbed out of my ballpoint pen... speaking of which...I need a new pen.... Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted October 18, 2010 Share Posted October 18, 2010 Was wondering when someone would reply about that. Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted October 18, 2010 Share Posted October 18, 2010 And here I was.... biting my tongue.... weiner. Do you know a guy named Ralph? Quote Link to comment Share on other sites More sharing options...
LARRY BRUDZYNSKI Posted October 18, 2010 Share Posted October 18, 2010 Ralph-Rex-Brad Just don't sit right......Please don't include BRAD in this...... Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted October 18, 2010 Author Share Posted October 18, 2010 I like the new regulator kit, however -- don't bother selling it on an E-series... see if you can get the spring seperately from ITEC -- that's the only part of the regulator kit you can use. Yeeeeeeeeeahhhh... but... More often than not when I test for and find a bad regulator it has nothing to do with the spring. I commonly find the rubber seal on the valve has come apart. I agree that the cover is basically not needed but the spring along with with new seals, valve and air bleed orifice really should be replaced. Quote Link to comment Share on other sites More sharing options...
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