Chickenman Posted November 7, 2017 Share Posted November 7, 2017 (edited) I would install the check valve first of all and see what that does. Without the check valve in the pump the Fuel Pressure will definitely drop. The FPR alone won't stop the pressure drop off. However, if I understand you correctly. After a 30 minute stop ( and Heat soak ) the fuel pressure only comes up to 10 psi. How long does that last? A heat soak issue ( fuel percolation ) should clear itself pretty fast. Within a minute or so maximum. It may be possible that the Fuel Pump is losing it's prime with out the check valve installed. Where is the fuel pump located? It should be at the rear of the car, close to the fuel tank and mounted as low as possible. Make sure the Fram G3 sure is not plugged or restricted. A 100 Micron filter ( Aeromotive makes a good pre-filter ) with a fairly large surface area will work well. Do not put in a Post pump filter ahead of the pump. These are typically 40 Micron or smaller and restrict fuel too much when used before the pump. Edit: Actually, thinking about it, the Fram G3 is a post pump filter. It is designed to be used under pressure.. not suction. With the added volume of the Bosch 044, sometimes the paper elements collapse. It also does not flow enough for you application. I'd have a close look at that G3 filter. Other possibilities. FPR may have a bit of debris stuck in the seat or the valve is sticking open. Take it apart and inspect. Aeromotive FPR are usually very high quality, but even the best quality parts are sometimes defective. Check for any kinks or restrictions in fuel lines. Another possibility, and this can be a SOB to find, is that the fuel tube in the Fuel tank feed is rusted and has perforations in it. This can suck air and cause the FP to olose prime. Usually happens below a certain fuel level in the tank. But the first thing I'd do is put that check ball back in place. Simple and it may do the trick... . Edited November 7, 2017 by Chickenman Quote Link to comment Share on other sites More sharing options...
Chickenman Posted November 7, 2017 Share Posted November 7, 2017 (edited) The surge tank wiring and plumbing also need looking at . The Carter scavenge pump should be on it's own separate Bosch relay ( Not on the MS relay board ) and needs twelve gauge wire as well. Where is the surge tank located. Again it should be located close to the fuel tank and as low as possible. All electrical pumps work best as pusher pumps. They do not work as well as puller pumps. The Surge tank should have a vent line leading back to the fuel tank. With out a vent line, you could create an air lock in the surge tank. One other thing. Does the Carter fuel pump have enough volume to keep up with the Bosch 044 pump? It must be able to supply MORE volume than the 044 can push out at maximum capacity... otherwise it just becomes a restriction and the surge tank will run low, causing cavitation in the Bosch 044 FP. Edited November 8, 2017 by Chickenman Quote Link to comment Share on other sites More sharing options...
seattlejester Posted November 8, 2017 Share Posted November 8, 2017 Echoing above, what's the carter fuel pump rated to? Do you have a fuel return back to your fuel tank once the surge tank fills? Can you hear it trickling back? Do you have a vent line back to the tank or to atmosphere? If the bosch pump pulls more then the carter pump you are going to have an imbalance in pressures if you have a sealed system for the most part. What kind of lines are you running? Have you checked the fuel filter? I know bosch pumps don't like a fine filter in front of them. Some people even suggest running without one for pump longevity. The check valve would keep fuel in the initial startup, but once the car is running if it continues to make 10psi then you have another problem somewhere. This is where video or pictures are worth a lot more. Are you running the bosch pump dry? Do you have a sock on the pump? Is it cavitating? Without the pictures and information this discussion really fair to try and have. Quote Link to comment Share on other sites More sharing options...
HuD 91gt Posted November 8, 2017 Share Posted November 8, 2017 His HP Bosch 044 should run through the FPR and have a return back to the surge tank. The frame G3 is filtering the fuel from the fuel tank, to the surge tank correct? It is filtering LP fuel from the carter pump. I don't see issues there. The LP fuel pump doesn't have to keep up with the 044 unless he is running the 044 to it's limits at all times and the surge tank is too small to be used as a buffer for changes in fuel burn. Make sure vent and return hoses from the surge tank and fuel tank are clear and make sense. Positive differentials between the two could cause you issues if they aren't venting properly. Despite how much thought and engineering I went in with my surge tank development, when I was filling up I was only able to get a 1/2 tank of fuel. I realized my venting was way off. Like they say above. Let's get some photo's of your whole system. Quote Link to comment Share on other sites More sharing options...
HuD 91gt Posted November 8, 2017 Share Posted November 8, 2017 Random thought. But how accurate are FPR gauges in the low end? I searched the Carter pump and it says it operates at 4-8psi. Pending how the surge tank is plumbed (Not the way I believe he had it in my post above), is it possible your 044 is not operating and the pressure you are seeing is directly from the Carter pump? Just a random thought, and it completely depends how your system is hooked up. Quote Link to comment Share on other sites More sharing options...
Chickenman Posted November 8, 2017 Share Posted November 8, 2017 (edited) 5 hours ago, HuD 91gt said: His HP Bosch 044 should run through the FPR and have a return back to the surge tank. The frame G3 is filtering the fuel from the fuel tank, to the surge tank correct? It is filtering LP fuel from the carter pump. I don't see issues there. The LP fuel pump doesn't have to keep up with the 044 unless he is running the 044 to it's limits at all times and the surge tank is too small to be used as a buffer for changes in fuel burn. Make sure vent and return hoses from the surge tank and fuel tank are clear and make sense. Positive differentials between the two could cause you issues if they aren't venting properly. Despite how much thought and engineering I went in with my surge tank development, when I was filling up I was only able to get a 1/2 tank of fuel. I realized my venting was way off. Like they say above. Let's get some photo's of your whole system. Sorry... but I disagree with that. The feed pump absolutely MUST keep up with the main pump under all conditions and keep the main pump submerged in the Surge tank. You run the Ffel level in the surge pump too low and the Bosch pump will cavitate and you can kiss it good bye in a hurry. But likely you will have melted a piston by then. Feed pump does not have to be high pressure. But it must be high volume. Think of a Surge tank as a float bowl. Yes, there is some reserve, but with a GT3076 and 550cc injectors you can suck a Surge tank down pretty fast. Also depends on mounting locations of pumps etc. Pictures will definitely help. G3 Fram filter is definitely a restriction on a motor of this potential. I've run into problems with a G3 pre-filter. on a hot day on my NA motor. Switching to a Aeromotive 100 Micron filter. BTW, have a look at the 280Z stock fuel line hose sizing to and from the Fuel pump. Inlet is 11mm ID ( 7/16" ) . Outlet from pump is 9mm ( 3/8" ) That should tell you something. The feed from the fuel tank to the scavenge ( or main pump ) pump and the feed from the scavenge pump should always be larger than the outlet size from the Main Pump. If Main pump is AN-6... inlet hose should be AN-8. Edited November 8, 2017 by Chickenman Quote Link to comment Share on other sites More sharing options...
Chickenman Posted November 8, 2017 Share Posted November 8, 2017 Quote from Aeromotive on this exact problem. Could definately be Pump cavitation. Quote 3.) After 30 minutes or so of driving, fuel pressure starts to fall, then the fuel pump gets louder and/or seems to quit running altogether. What’s wrong, is my pump going bad? You may be experiencing EFI vapor lock. Even though the fuel is recycling through the car, eliminating localized hot spots, the recycled fuel is still being exposed to under-hood engine heat. Fuel in an EFI bypass system does slowly warm up as it is recycled through the chassis, the fuel rail(s), engine compartment, and finally back to the tank. The longer an EFI engine runs, the higher fuel tank temperatures can become. Unlike the more common carburetor vapor lock, where fuel is heated to boiling in the float bowl(s) or fuel line(s) under the hood, EFI vapor lock is often caused by hot fuel in the tank. Excessive pump noise along with fluctuating or dropping fuel pressure often indicate that fuel temperature is high enough to cause hot fuel handling problems. A combination of high fuel temperature and low pressure can result in cavitation, where liquid fuel changes to vapor. In a return style EFI fuel system, the most likely place for these conditions to exist in the same place, at the same time, is at fuel pump inlet. Once cavitation starts, it will feed upon itself. As vapor enters the pump, it displaces liquid fuel required to lubricate the mechanism, allowing metal to touch metal, creating even more friction and heat. Once the pump begins to super heat, a complete vapor lock will develop. In order to prevent cavitation and vapor lock, correct fuel system design and installation are vital. Ensure supply lines and inlet filters meet hi-flow, low restriction requirements and are kept clean. Keep the tank full on hot days. Reduce fuel pump speed and recycle rate with a fuel pump speed controller during low load, idle and cruise conditions. Carefully route fuel lines and plan component placement to avoid exhaust heat. Do not overlook proper tank ventilation, if the vent line or vent valve do not allow ample air to move freely in both directions, fuel delivery problems will never fully resolve. Any conditions that restrict the pump’s access to fuel in the tank must be addressed. For more detailed information on installation issues that can result in premature cavitation, hot fuel handling problems and vapor lock, see Aeromotive Tech Bulletins TB-101, TB-102 and TB-802, all of which can be found at www.aeromotiveinc.com under the Tech Help, Tech Bulletin section. I would definitely be looking at replacing that G3 and checking hose sizes. Further info on Pre-Filter restrictions. Read this: http://aeromotiveinc.com/wp-content/uploads/2014/12/TB_101_InletFilter02.pdf Quote Link to comment Share on other sites More sharing options...
Chickenman Posted November 8, 2017 Share Posted November 8, 2017 1 hour ago, HuD 91gt said: Random thought. But how accurate are FPR gauges in the low end? I searched the Carter pump and it says it operates at 4-8psi. Pending how the surge tank is plumbed (Not the way I believe he had it in my post above), is it possible your 044 is not operating and the pressure you are seeing is directly from the Carter pump? Just a random thought, and it completely depends how your system is hooked up. That is a possibility. Relay could be overheating on Relay Board. May have Thermal protection and relay is opening. Or some other intermittent electrical disruption. Or Bosch pump is cavitating badly and it takes a while to cool it down. Pump cavitation can do nasty things to a pump in short order. Fortunately the Bosch 044 is a roller vane design, which are much more robust than a Ceramic Turbine design. Quote Link to comment Share on other sites More sharing options...
seattlejester Posted November 8, 2017 Share Posted November 8, 2017 Yea without pictures/video/audio this is rough. Looking it up an 044 pump will push 4LPM. Depending on the surge tank size and design that might be too much. I've seen kits in the past where people used oil filters as surge tanks. While it works you could empty it before it started refilling to capacity if you weren't careful. Also without seeing the surge tank setup one can only guess how it is pulling fuel. I've seen some pneumatic pump designs where the suction is so strong and the tank material so weak that it pulled the bottom of the tank towards the pump inlet and cut off flow. When you shut the pump off it would relax. Took forever to find out what was going on. Quote Link to comment Share on other sites More sharing options...
HuD 91gt Posted November 9, 2017 Share Posted November 9, 2017 4 hours ago, Chickenman said: Sorry... but I disagree with that. The feed pump absolutely MUST keep up with the main pump under all conditions and keep the main pump submerged in the Surge tank. You run the Ffel level in the surge pump too low and the Bosch pump will cavitate and you can kiss it good bye in a hurry. But likely you will have melted a piston by then. Feed pump does not have to be high pressure. But it must be high volume. Think of a Surge tank as a float bowl. Yes, there is some reserve, but with a GT3076 and 550cc injectors you can suck a Surge tank down pretty fast. Also depends on mounting locations of pumps etc. Pictures will definitely help. G3 Fram filter is definitely a restriction on a motor of this potential. I've run into problems with a G3 pre-filter. on a hot day on my NA motor. Switching to a Aeromotive 100 Micron filter. BTW, have a look at the 280Z stock fuel line hose sizing to and from the Fuel pump. Inlet is 11mm ID ( 7/16" ) . Outlet from pump is 9mm ( 3/8" ) That should tell you something. The feed from the fuel tank to the scavenge ( or main pump ) pump and the feed from the scavenge pump should always be larger than the outlet size from the Main Pump. If Main pump is AN-6... inlet hose should be AN-8. If the return from the injectors goes back into the surge tank it will not matter if the LP pump can outflow the HP pump. Any residual fuel which is not used by the engine will be returned to the surge tank (Which 70+% of the time is a majority of the fuel pumped). In addition to this return fuel, will be the fuel supplied from the LP pump from the fuel tank. As long as the LP pump can supply enough GPH for the engine to use, the surge tank will never be low no matter the size of the HP pump. If the LP pump could not keep up with the GPH required by the engine then you would start to see the level of the surge tank decrease. Since the engine is never operating at max power 100% of the time, as long as the surge tank is large enough, and of a decent design it offers a buffer. But besides that point the Carter P4070 is a high flow LP pump. Pumping around 72GPH. Plenty to feed this setup in it's current tuning state i'm sure. Quote Link to comment Share on other sites More sharing options...
seattlejester Posted November 9, 2017 Share Posted November 9, 2017 What we have so far.... "My fuel system is Tank>>Fram G3 fuel filter>>Carter Fuel Pump (wired to my EZ Wiring kit, no relay, 14 gauge wire)>>External Surge Tank with submerged Bosch 044 (Wired to the MS Relay Board)>> Engine>> External Surge Tank>> Tank." What we really need to know: Flow: Stock tank > hose (size) > Fram G3 fuel filter > hose (size) > Carter Fuel pump > hose (size) > external surge tank (model, link, picture) > inlet mechanism (sock, fitting, sump) > bosch 044 pump > hose (3/16) > fuel rail in (fitting size) > fuel rail > fuel rail out (fitting size) > hose (size) > aeromotive fpr inlet (fitting size) > aeromotive fpr > aeromotive outlet (fitting size) > hose (size) > surge tank > hose (size) > fuel tank. Vent: Then we need to know the vent situation. The surge tank should have a vent, and the fuel tank should have a vent. Then the electrical. What Hud brings up is interesting. If the bosch 044 pump is blowing the fuse and not working and your fuel rail is only showing 10psi, you might be seeing the carter pump pushing fuel. The problem with that then is the surge tank is not doing what it should be doing if you are generating pressure that means you are filling up the surge and pushing fuel past the bosch pump which shouldn't happen, it should just be returning to the fuel tank. Quote Link to comment Share on other sites More sharing options...
Chickenman Posted November 15, 2017 Share Posted November 15, 2017 Further reading on Fuel Pump Cavitation and starvation caused by restrictive Pre-Pump filters. http://aeromotiveinc.com/wp-content/uploads/2014/12/TB_101_InletFilter02.pdf http://aeromotiveinc.com/wp-content/uploads/2014/12/TB_802_Tanks_Sumps_Stealth_02.pdf Aeromotive has some excellent Tech Articles. Well worth reading them all. https://www.aeromotiveinc.com/tech-help/tech-bulletins/ Quote Link to comment Share on other sites More sharing options...
Chickenman Posted November 15, 2017 Share Posted November 15, 2017 Holy Hanna... I finally found some specs on Fram G3 filters. They are rated at 5 Microns. That's far too small to be used as a pre-filter for ANY EFI pump. Let alone a high volume pump such as a Bosch 044. Get rid of the G3 and put in a recommended Aeromotive pr pump filter which are 100 Microns in size. Fine filters should only be installed post pump. Thanks Atlantic Z for perpetuating this incorrect information. I was wondering about this ever since I installed a Fram G3 before my Airtex 8312 EFI pump based on the Atlantic Z article.. It's a Ceramic turbine pump, so it does need a pre-filter according to Airtex. In Tank pumps have a sock to catch the coarse stuff, but an inline pump doesn't. Would have been nice if Airtex had recommended a proper inline Pre-filter... but they don't. My pump had been getting growly and noisy during hot weather. Worse when fuel tank was below 1/2. Mkaes sense now as this is a Textbook case of a restrictive fuel filter being installed before the pump ( Fram G3 ) . G3 is going bye bye and I'm ordering a proper Aeromotive 100 Micron SS filter from Summit ASAP!!! Quote Link to comment Share on other sites More sharing options...
ZHoob2004 Posted November 15, 2017 Share Posted November 15, 2017 To add some further confirmation of the prefilter problem, I had cavitation issues using a stock 280z fuel pump with a Napa 3003 (WIX 33003), which is 20 micron Quote Link to comment Share on other sites More sharing options...
dpuma8 Posted November 20, 2017 Author Share Posted November 20, 2017 Been busy with my kids' sports and family visiting but here is at least a picture of my setup. This all is mounted in stock location. The feed hoses are 3/8" and the outside return lines are 5/16". Removed both G3 filters. Quote Link to comment Share on other sites More sharing options...
seattlejester Posted November 23, 2017 Share Posted November 23, 2017 That is a very small surge tank. Quote Link to comment Share on other sites More sharing options...
Chickenman Posted November 23, 2017 Share Posted November 23, 2017 ^ It's a very well proven design by Integrated Engineering. No reported issues that I have ever read from BT Audi/VW forums. Quote Link to comment Share on other sites More sharing options...
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