94RX74me

I recently purchased a 94 RX7 with a 20B. It has twin 290lph Denso fuel pumps, the CJM twin fuel pump assembly and it was all professionally installed in 2012 by Forged Performance out of Atlanta.


The other day I noticed that the relays for the fuel pumps get very hot. I was hoping there was just a bad ground or wires touching that was causing the issue. I checked the wires and they all look ok. I cleaned the grounding point in the hatch area and bolted it back down - still the relays get very hot.


I am much better with mechanical stuff than electrical problems so I am at a loss as to what to try. I'd like to at least try a few things before bringing it to an automotive electrical repair place. Any constructive input would be greatly appreciated.

Sgtblue

iTrader: (16)

Like you, I'm not versed in things electrical. Not sure how many running a 20b come to this section. If you don't get a lot of experienced response you might try a search here 20B Forum - RX7Club.com for some threads on the subject.

94RX74me

Quick update. I pulled the pumps out of the tank tonight. I thought maybe they were mounted too low and were not able to pull fuel due to touching the bottom of the tank. My measurements show that is not the issue. Looking at the filters on the bottom of the pumps - they were really dirty. It took me a while to find replacements. I will install them tomorrow. It is possible that they were they were so plugged up that they were causing resistance/heat in the relays. I'll report what I find out tomorrow.

misterstyx69

iTrader: (142)

just to toss this out there..
If you are running a lower Amp relay..say a 40,you can try to upgrade to a 50 and see if that takes care of the heat on the relay.
Also,the gauge of wire supplying the fuel system may want to be looked into or upgraded too.

94RX74me

Where should I look for a larger relay? That is actually the first thing I tried. I sent my son to NAPA with the relays that go to the two pumps. Not sure what amp they are but they are a about 1 inch by 1 inch square. NAPA did not have larger relays with the proper 4 prong configuration. If you have any suggestions as to where I should look for larger relays, please let me know.


As far as the wiring, the relays have a larger gauge wire leading to them than what is coming from the pumps. That is the correct way to do it from what I've been told.

misterstyx69

iTrader: (142)

You can google "50 amp relay" and get literally 1000's of hits on that.
I got mine at an Auto supply store.
Napa is not the only store in the world to deal and can sometimes hinder what you want to get when searching.They don't have an Effin clue as to why the engine has 2 different sets of plugs!,and most of them have students or young guys just there to work for beer money!(in my Opinion!.)

Take one relay out...go to parts store..Say"HEY..I want a bigger amp relay than THIS!"..
If the guy bobbles his head.looks like an Owl and says "Orelaaaay">..then walk away! :p

max0911

iTrader: (1)

Maybe this diagram will help you verify if everything is set up properly and you can always solder the wires directly on the relay to avoid connector issues.

How to solder to a relay



With a quick search on google I was able to find the amp draw of the denso pump in relation to gas pressure. A 40 AMP relay seems to be enough for 2 denso pumps.

94RX74me

The reply above is fantastic. It also shows what I think may be the problem... I installed the new "sock filters" on the pumps tonight. I also shortened the length that the pumps were hanging by about a half inch because they were very close to the bottom of the tank. My rationale for the above was the filters were dirty - I thought the restriction could cause the relays to heat up. Also, I thought since the filters were located so low (touching the bottom of the tank) possibly there was a restriction there. Unfortunately these changes did not make the situation better. I started looking at the wiring again which is difficult since it is in that black corrugated protective stuff. What I found is that the fused wires at the batter are about 16 gauge. They attach to what looks like 14 gauge. Then finally there is what looks like 12 gauge that ultimately leads to the relay. My guess is it may be the starting with 16, then going to 14 then finally ending in 12 gauge wire that is causing things to heat up. I also noticed that the fuses in the 16 gauge wire are hot as well. Tomorrow I will switch the wires coming from the battery and going to the relays to 10 gauge. Hopefully that will solve the problem. Thanks to all for your input!

94RX74me

I'm not the kind of guy that flames vendors on public forums, but I have to say that Forged Performance, LLC in Marietta did less than a stellar job of installing/wiring the pumps on this car. I purchased the car and with it came a stack of receipts for parts and work done. One of the receipts is for $2048 worth of fuel pumps and labor to install them. The wiring to the relays on this car was a joke. In-line fuse with 16 gauge wire connected to a foot of 14 gauge wire and then to 12 gauge wire to the relay. I have replaced all of that with 10 gauge wire. The in-line fuses used to get very hot. Now, with the proper size wire they do not heat up. The relays are still warm but not hot like they were. I need to replace the wire coming from the relay that goes to the pump as that is 12 gauge rather than the recommended 10 gauge.


I was also not impressed to find a hose clamp and other metal shavings in the fuel tank. Maybe Forged Performance, LLC did not put those there but I am surprised they did not notice/remove this stuff when they charged the prior owner over $2000 to do this work.


Thanks to all for your input on this issue.

RotaryEvolution

iTrader: (30)

denso pumps draw a lot of amps, i'd suggest replacing with larger relays or using dual relays for each pump so that they split the load(yes, 4 relays).

DC5Daniel

iTrader: (10)

Unfortunately Forged has developed quite the bad rap over the years (if you're local and in the community the stories come out). They have HUGE blowouts on major forums and then cover them up/hush the complainants. Their best sales reps and techs all left and went to competing shops. Two major stories that come to mind and are documented on the Internet involve a G35/37 (can't remember which) and a GTR.