questtuner82 Posted August 8, 2014 Report Share Posted August 8, 2014 Ok so I'm having what seems to be a fuel issue and I'd like to find out if my 87 quest is supposed to have vacuum to the fuel pressure regulator at idle or if it only receives pressure in boost to raise the fuel pressure in boost Link to comment Share on other sites More sharing options...
scott87star Posted August 8, 2014 Report Share Posted August 8, 2014 (edited) Odd, now that I look at a stock TB I see the regulator reference signal (hose) is on the upstream side of the throttle plate. So no, it won't see any vacuum at idle. That isn't how I did my MPI car and I'll be changing that on my TBI build so it is vacuum referenced but the factory ECU is using it without. Did you get a look at your fuel pressure when its running poorly yet? Edited August 8, 2014 by scott87star Link to comment Share on other sites More sharing options...
StarquestRescue Posted August 8, 2014 Report Share Posted August 8, 2014 Odd, now that I look at a stock TB I see the regulator reference signal (hose) is on the upstream side of the throttle plate. So no, it won't see any vacuum at idle. That isn't how I did my MPI car and I'll be changing that on my TBI build so it is vacuum referenced but the factory ECU is using it without.That is because the tbi injectors are on the same side of the throttle plate. It is quite possible to have 10 psi or more above the throttle plate and maybe 1 or 2 below when the throttle is barely open. This is especially true on a small turbo tbi car, The injectors must spray into what ever pressure is above the throttle plate on a tbi car. Link to comment Share on other sites More sharing options...
Dad Posted August 8, 2014 Report Share Posted August 8, 2014 Just tested with vac gauge. no vac at regulator at idle. Link to comment Share on other sites More sharing options...
ucw458 Posted August 9, 2014 Report Share Posted August 9, 2014 TBI cars don't need a vacuum source to the regulator. Only cars with injectors exposed to vacuum like a MPI setup will need a vacuum source to the regulator. It's all about pressure balancing. Inside and outside the manifold. Injectors have a minimum pressure they need to operate properly. Usually around 35-45 PSI. Now if your engine is running at 20 lbs of boost and you are only feeding the injectors 40 psi then they will act like you are feeding them 20 psi and not spray properly. The boost pressure will cancel out some of the fuel pressure. That's why boosted cars use a rising rate fuel pressure regulator. The reverse is also true. On a TBI car the injector is before the throttle body so the injector nozzle never sees vacuum only boost. But in a MPI setup the injector nozzle is exposed to manifold vacuum at idle and cruising. That vacuum can make the injector act like you are feeding it 50-60 PSI even though your regulator is set to 40 psi. You don't need the extra fuel at those times that a higher pressure delivers. It can make idle and cruise tuning on large injectors difficult. So on those setups the regulator gets a vacuum source so the regulator can lower fuel pressure to balance the system. Link to comment Share on other sites More sharing options...
scott87star Posted August 9, 2014 Report Share Posted August 9, 2014 Y'all are very correct, never thought about the differences between a setup upstream or downstream of the throttle plate. But the engineers put the reference right next to where the fuel is injected. Link to comment Share on other sites More sharing options...
questtuner82 Posted August 9, 2014 Author Report Share Posted August 9, 2014 Scott, still haven't figured out what's going on, but as for fuel pressure, I have 35 lbs at idle and it does raise in boost to 42-42 lbs but then falls like the fuel pump just shuts off. This is getting very frustrating now. Fuel pump is new everything in the fuel system is basically new. The ign system is new. Not sure where to go with all this. I also have a known good ecu and knock box coming to me Monday or Tuesday. Buddy of mine had them and took them out of his car for Mpi and edis swap. So what should I look for now with this headache I have that's supposed to be a car? It's getting close to going to the shredder Link to comment Share on other sites More sharing options...
ucw458 Posted August 9, 2014 Report Share Posted August 9, 2014 If you left the stock cone filter in the pump inlet then take it out and throw it away. It restricts the inlet on aftermarket pumps and starves them of fuel under boost. Also check for proper voltage at the pump. The stock wiring could be degraded and not powering the pump correctly. Link to comment Share on other sites More sharing options...
scott87star Posted August 9, 2014 Report Share Posted August 9, 2014 I have 35 lbs at idle and it does raise in boost to 42-42 lbs but then falls like the fuel pump just shuts off. Well there is the problem, well done! Don't get depressed over it, fix it. Do the things UCW suggests. Link to comment Share on other sites More sharing options...
StarquestRescue Posted August 9, 2014 Report Share Posted August 9, 2014 The op's needs to start with a new in tank filter in addition to checking the suction hose for obstructions. If a aftermarket filter was installed in the suction hose that would also be an obstruction. If the op's new pump was installed before the car set for two years it is not really new any more. But since the pump can keep up for the first 20 mimits, that also points to crap in the tank getting drawn to the in tank filter and blocking it. In a case like that, when the pump is shut off, the crap falls off the filter and the car may run better again for a short while. Link to comment Share on other sites More sharing options...
questtuner82 Posted August 9, 2014 Author Report Share Posted August 9, 2014 Yes the pump is 2 years old but the car only ran 80 miles on it. Also the pickup is new no filter prior to the fuel pump except the one in the tank. The tank was replaced due to inside rust and all the fuel lines were flushed/blown out when all was installed new filter under hood and injectors were sonic cleaned and flowed. Relay was placed in the car for the fuel pump and all wiring was checked and ran as supposed to be with the f/p relay upgrade for the Wally 255 is the fuel pump controlled by the ecu? Could my ecu be bad or the knock box? Does the knock box control anything in the fuel dept? Link to comment Share on other sites More sharing options...
StarquestRescue Posted August 9, 2014 Report Share Posted August 9, 2014 is the fuel pump controlled by the ecu? Only in that the ecu must see an rpm signal. The pump is either on or off. It can be run from the test plug as a temporary test. Could my ecu be bad or the knock box? No, it is a fuel pump or filter problem. Does the knock box control anything in the fuel dept. No The symptoms point to a in tank filter and or fuel pump problem. Things like gas and fuel pumps sometimes go bad when they set. Bad gas clogs fuel filters. Link to comment Share on other sites More sharing options...
questtuner82 Posted August 9, 2014 Author Report Share Posted August 9, 2014 Ok so I understand that there could be something obstructing the fuel flow somewhere and could be cause for this issue but could there be anything else that would cause sudden fuel pressure loss only in boost for the second it drops off? It has a steady 35psi at idle from cold start all the way through 45 mins of testing. I tested fuel psi in boost cold and hot runs and it will raise in boost but falls off for a brief second to like 15 psi then comes back up. Also what should be volt/ amp readings be at pump at idle and in boost? I get a 12.8 volt at idle and 13.2 when I rev the car. Does this sound about right? I'm going to change the filter in tank and under the hood again. Also I may put the factory f/p back in it as I know it is still good. One thing though on the factory pump it has a diaphragm looking thing on it and a banjo fitting which I no longer have. Can I just run the output feed directly like the Wally 255 is now without the diaphragm? Link to comment Share on other sites More sharing options...
ucw458 Posted August 9, 2014 Report Share Posted August 9, 2014 Are you sure you got a real walbro? Chinese knockoffs look real but can have reduced performance. The part on the end of the stock pump is an external check valve. You can run the pump without it. The voltage sounds right. You said you put in a relay. Do you mean you did the pump re-wire? If you have a spare regulator I would try switching them to see if the fuel pressure improves. Link to comment Share on other sites More sharing options...
questtuner82 Posted August 10, 2014 Author Report Share Posted August 10, 2014 Ok so I changed filters and changed fuel pressure regulator with all new and still doing the same thing. Fuel pressure drops down to 15 psi in boost for a brief minute. All volt checks to fuel pump is great. And yes I did the f/p rewire Link to comment Share on other sites More sharing options...
scott87star Posted August 10, 2014 Report Share Posted August 10, 2014 Replace the fuel pump. Link to comment Share on other sites More sharing options...
markhansenconquest Posted August 10, 2014 Report Share Posted August 10, 2014 Put in clear filter before pump to replace cone filter and see what shows up...........autozone ...dura last brand # FF3-8DL-3/8 " USE hose clamps its not metric...then change out with metal one ...don't trust plastic for long term..... Link to comment Share on other sites More sharing options...
ucw458 Posted August 10, 2014 Report Share Posted August 10, 2014 Replace the fuel pump. this Link to comment Share on other sites More sharing options...
StarquestRescue Posted August 10, 2014 Report Share Posted August 10, 2014 Ok so I changed filters with all new.I am sorry, but i have to ask this. Where did you get a new factory in tank filter on a weekend? The parts store do not have those, they are dealer only. Link to comment Share on other sites More sharing options...
StarquestRescue Posted August 10, 2014 Report Share Posted August 10, 2014 Put in clear filter before pump to replace cone filter and see what shows up...........autozone ...dura last brand # FF3-8DL-3/8 " USE hose clamps its not metric...then change out with metal one ...don't trust plastic for long term.....You know another guy had a similar problem a month ago. The problem was from using an aftermarket filter pre pump. http://www.starquestclub.com/forum/index.php?showtopic=143523&st=20 Link to comment Share on other sites More sharing options...
ucw458 Posted August 10, 2014 Report Share Posted August 10, 2014 Put in clear filter before pump to replace cone filter and see what shows up...........autozone ...dura last brand # FF3-8DL-3/8 " USE hose clamps its not metric...then change out with metal one ...don't trust plastic for long term..... Filters before the pump can cause fuel starvation and cavitation. Cavitation can kill fuel pumps very quickly. Fuel starvation can kill motors very quickly. A strainer on the pickup in the tank is all you need. Anything finer than that causes problems. Link to comment Share on other sites More sharing options...
questtuner82 Posted August 11, 2014 Author Report Share Posted August 11, 2014 Ok so I drained all my fuel in a 5micron filter today from the tank. All crystal clear nothing as of debris. Dropped the tank and looked inside all clean and new. FYI it was a brand new tank 2 years ago. This car part place that sells everything had a lot of nos parts for this car. Paid 375$ for a new tank 100$ for new pickup and 75$ for new sender. Anyways I do not have a filter before the f/p other than the in tank pre-filter. I installed a new airtex e8000 fuel pump. O/e spec pump and new filter under hood. Blew all the fuel lines out and all clear also did a t/b rebuild/refresh kit and new fuel pressure regulator. And still same exact thing is happening. Losing fuel pressure down to 15psi in boost for a brief 2 seconds then comes back up to 42-45 psi. At a complete loss of what to do/check for now. Also swapped the knock box out and ecu. Same thing. Today I noticed that when it is doing this, missing, backfiring, popping it is dumping heavy black smoke out of the exhaust. Also after a hard run bc I'm getting really p/o the exhaust manifold exhaust side of turbo and down pipe was glowing cherry red. I don't have a wideband or a/f gauge in it yet but will soon. I now have a fuel gauge in my pillar pod along with my boost gauge and have room for another 2 gauges. But soon this car is going to the scrap yard if I can't get it figured out. Is there anybody local to me? I live in Pittsburgh pa. I need somebody local to help me out Link to comment Share on other sites More sharing options...
StarquestRescue Posted August 11, 2014 Report Share Posted August 11, 2014 Wire a 12v indicator light to the fuel pump test plug by the air filter and tape it to the dash. If the power to the pump is interrupted while the car is running the light will blink out. Link to comment Share on other sites More sharing options...
ucw458 Posted August 11, 2014 Report Share Posted August 11, 2014 Today I noticed that when it is doing this, missing, backfiring, popping it is dumping heavy black smoke out of the exhaust. Also after a hard run bc I'm getting really p/o the exhaust manifold exhaust side of turbo and down pipe was glowing cherry red. Now that's a totally different symptom that points in a different direction. I would check your injectors for proper spray pattern. Make sure the fuel pressure regulator FPR isn't leaking into the TB by doing a vacuum test on the line going to it. It should hold vacuum indefinitely. Make sure your base timing is 10 deg BTDC and that the vacuum advance and mechanical advance are working properly. If all that is working properly you may want to try swapping ECUs. Yours could have an issue. It's unlikely and a shot in the dark because I haven't heard of many ECUs going bad. But they are all at least 25+ years old now. Link to comment Share on other sites More sharing options...
questtuner82 Posted August 11, 2014 Author Report Share Posted August 11, 2014 Ok so the guy that bought my parts car brought me his ecu and his knock box this morning. The fuel pressure regulator holds vacuum as I checked it this morning and we put a timing light on it and it is dead nuts 10btdc. The dizzy is a remanned one and is for turbo applications as I checked before I ordered it. My old dizzy was still good but I got a new one just incase it was bad. The injectors seem to be fine. I took the charge pipe off at the tb and ran it at idle and primary sprays nice then I swapped inj plug to secondary and it sprays nice too. And the car ran pig rich on the secondary inj. Is there anybody that's local to me that is willing to take a look and help me figur this thing out? Link to comment Share on other sites More sharing options...
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